Novel Pyrimidine Derivatives Field of the invention The present invention relates to S1P1/EDG1 receptor agonists of formula (I) and their use as active ingredients in the preparation of pharmaceutical compositions. The invention also concerns related aspects including processes for the preparation of the compounds, pharmaceutical compositions containing a compound of the formula (I), and their use as compounds improving vascular function and as immunomodulating agents, either alone or in combination with other active compounds or therapies. Background of the invention The human immune system is designed to defend the body against foreign micro-organisms and substances that cause infection or disease. Complex regulatory mechanisms ensure that the immune response is targeted against the intruding substance or organism and not against the host. In some cases, these control mechanisms are unregulated and autoimmune responses can develop. A consequence of the uncontrolled infiammatory response is severe organ, cell, tissue or joint damage. With current treatment, the whole immune system is usually suppressed and the body's ability to react to infections is also severely compromised. Typical drugs in this class include azathioprine, chlorambucil, cyclophosphamide, cyclosporin, or methotrexate. Corticosteroids which reduce inflammation and suppress the immune response, may cause side effects when used in long term treatment. Nonsteroidal anti-infammatory drugs (NSAIDs) can reduce pain and inflammation, however, they exhibit considerable side effects. Alternative treatments include agents that activate or block cytokine signaling. Orally active compounds with immunomodulating proporties, without compromising immune responses and with reduced side effects would significantly improve current treatments of uncontrolled inflammatory disease. In the field of organ transplantation the host immune response must be suppressed to prevent organ rejection. Organ transplant recipients can experience some rejection even when they are taking immunosuppressive drugs. Rejection occurs most frequently in the first few weeks after transplantation, but rejection episodes can also happen months or even years after transplantation. Combinations of up to three or four medications are commonly used to give maximum protection against rejection while minimizing side effects. Current Standard drugs used to treat the rejection of transplanted organs interfere with discrete intracellular pathways in the activation of T-type or B-type white blood cells. Exampies of such drugs are cyclosporin, daclizumab, basiliximab, everolimus, or FK506, which interfere with cytokine release or signaling; azathioprine or leflunomide, which inhibit nucleotide synthesis; or 15-deoxyspergualin, an inhibitor of leukocyte differentiation. The beneficial effects of broad immunosuppressive therapies relate to their effects; however, the generalized immunosuppression which these drugs produce diminishes the immune system's defense against infection and malignancies. Furthermore, Standard immunosuppressive drugs are often used at high dosages and can cause or accelerate organ damage. Description of the invention The present invention provides novel compounds of formula (1) that are agonists for the G protein-coupled receptor S1P1/EDG1 and have a powerful and long-lasting immunomodulating effect which is achieved by reducing the number of circulating and infiltrating T- and B-lymphocytes, without affecting their maturation, memory, or expansion. The reduction of circulating T- / B-lymphocytes as a result of S1P1/EDG1 agonism, possibly in combination with the observed improvement of endothelial cell layer function associated with S1P1/EDG1 activation, makes such compounds useful to treat uncontrolled inflammatory disease and to improve vascular functionality. The compounds of the present invention can be utilized alone or in combination with Standard drugs inhibiting T-cell activation, to provide a new immunomodulating therapy with a reduced propensity for infections when compared to Standard immunosuppressive therapy. Furthermore, the compounds of the present invention can be used in combination with reduced dosages of traditional immunosuppressant therapies, to provide on the one hand effective immunomodulating activity, while on the other hand reducing end organ damage associated with higher doses of Standard immunosuppressive drugs. The observation of improved endothelial cell layer function associated with S1P1/EDG1 activation provides additional benefits of compounds to improve vascular function. The nucleotide sequence and the amino acid sequence for the human S1P1/EDG1 receptor are known in the art and are published in e.g.: HIa, T., and Maciag, T. J. Biol Chem. 265 (1990), 9308-9313; WO 91/15583 published 17 October 1991; WO 99/46277 published 16 September 1999. The potency and efficacy of the compounds of formula (I) are assessed using a GTPyS assay to determine ECso values and by measuring the circulating lymphocytes in the rat after oral administration, respectively (see in Examples). i) The invention relates to novel pyrimidine compounds of the formula (I) wherein the asterisks indicate the bond that is linked to the pyrimidine group of formula (I); R^ represents Ci.4-alkoxy, Ci.4-alkylamino, N-Ci.4-alkyl-N-Ci.3-alkylamino, C3.5-cycloalkyiamino, Cs-s-cycioalkylmethylamino, pyrrolidine (such as pyrroiidin-1-yl), or piperidine; R2 represents Ci.2-alkyl or C3-4-alkyi; R3 represents hydrogen, C1-4-alkyl, or C1-3-alkoxy; R4 represents hydrogen, C1-4-alkyl, or C1-3alkoxy; 4 R1 represents 2,3-dihydroxypropyl, di-(hydroxy-C1-4-alkyl)-C1-4 -alkyl, -CH2-(CH2)k-NHSOR53, -(CH2)nCH(OH)-CH2-NHSO2R53 -CH2-(CH2)K-NHCOR54, -(CH2)nCH(OH)-CH2-NHCOR6, -CH2-(CH2)n-CONR51R52 1-(3-carboxy-azetidinyl)-2-acetyl, 1-(2-carboxy-pyrrolidinyl)-2-acetyl, 1 -(3-carboxy-pyrrolidinyl)-2-acetyl, 1 -(3-carboxy-azetidinyl)-3-propionyl, 1 -(2-carboxy-pyrrolidinyl)-3-propionyl, 1 -(3-carboxy-pyrrolidinyl)-3-propionyl, -(CH2)nCH(0H)-CH2-NR51'R52 hydroxy-C2-5-alkoxy, di-(hydroxy-C1-4-alkyl)-C1-4-alkoxy, 2,3-dihydroxy-propoxy (such as preferably (S)-2,3-dihydroxy-propoxy), 2-hydroxy-3-methoxy-propoxy, -OCH2-(CH2)m-NR51R52 2-[(a2etidine-3-carboxylic acid)-1-yl]-ethoxy, 2-[(a2etidine-3-carboxylic acid Ci.5-alkylester)-1-yl]-ethoxy, 2-[(pyrrolidine-3-carboxylic acid)-1-yl]-ethoxy, 2-[(pyrrolidine-3-carboxylic acid C1-5-alkylester)-1-yl]-ethoxy, -0CH2-CH(0H)-CH2-NR51R52 3-[(azetidine-3-carboxylic acid)-1-yl]-2-hydroxypropoxy, 3-[(azetidine-3-carboxylic acid C1-5-alkylester)-1 -yl]-2-hydroxypropoxy, 2-hydroxy-3-[(pyrrolidine-3-carboxylic acid)-1 -yl]-propoxy, 2-hydroxy-3-[(pyrrolidine-3-carboxyiic acid Ci.5-alkyiester)-1-yl]-propoxy, 2-hydroxy-3-[{pyrrolidine-2-carboxylic acid)-1 -yl]-propoxy, 2-hydroxy-3-[{pyrrolidine-2-carboxylic acid Ci.5-alkylester)-1-yi]-propoxy, -OCH2-(CH2)m-NHS02R53 -0CH2-CH(0H)-CH2-NHSO2R53, -OCH2-(CH2)m-NHCOR54 or -OCH2-CH(OH)-CH2-NHCOR54 (wherein the carbon atom to which the hydroxy group is attached is preferably in the S-configuration); R51 represents hydrogen, C1-3-alkyl, 2-hydroxyethyl, 2-hydroxy-1-hydroxymethyl-ethyl, 2,3-dihydroxypropyl, carboxymethyl, (Ci-5-alkylcarboxy)methyl, 2-carboxy6thyl, 2-(Ci.5-alkylcarboxy)ethyl, or 2-aminoethyl; R*^ represents hydrogen, methyl, or ethyl; R^^ represents C, 3-alkyl, methylamino, ethylamino, or dimethylamino; R54represents hydroxy-C1-2-alkyl or R51R52N-C1-2-alkyl; R55 and R56 independently represent hydrogen or methyl; k represents the integer 1, 2, or 3; m represents the integer 1 or 2; n represents 0,1, or 2; and R® represents hydrogen, Ci.4-alkyl, or halogen. The general terms used hereinbefore and hereinafter preferably have, within this disclosure, the following meanings, uniess otherwise indicated: The term Cx.y-alkyl, x and y being an integer, means saturated, branched or straight chain alkyl groups with x to y carbon atoms. Likewise, the term C1-4-alkyl means saturated, branched or straight chain alkyl groups with one to four carbon atoms. Examples of C1.4-alkyl groups are methyl, ethyl, n-propyl, /so-propyl, n-butyl, and /so-butyl (preferably methyl, ethyl, n-propyl, /so-propyl, or /so-butyl). Likewise, the term C1-5-alkyl means saturated, branched or straight chain alkyl groups with one to three carbon atoms. Examples of C1-3-alkyl groups are methyl, ethyl, n-propyl, and /so-propyl (preferably methyl, or ethyl). The term Cx-y-alkoxy means a R-O group, wherein R is a Cxy-alkyl. Examples of C1-4-alkoxy groups are methoxy, ethoxy, n-propoxy, /so-propoxy, and /so-butoxy. The term Ca-s-cycloalkyl refers to a saturated cyclic hydrocarbon ring system with 3 to 5 carbon atoms, i.e. cyclopropyl, cyclobutyl, or cyclopentyl. The term halogen means fluoro, chloro, bromo or iodo (preferably fluoro or chloro; especially preferred chloro). ii) A further embodiment of the invention relates to pyrimidine derivatives according to embodiment i), wherein A represents wherein the asterisks indicate the bond that is linked to the pyrimidine group of formula (I). iii) Another embodiment of the invention relates to pyrimidine derivatives according to embodiment i), wherein A represents wherein the asterisks indicate the bond that is linked to the pyrimidine group of formula (1). iv) Another embodiment of the invention relates to pyrimidine derivatives according to embodiment i), wherein A represents wherein the asterisk indicates the bond that is linked to the pyrimidine group of formula (I). v) Another embodinnent of the invention relates to pyrimidine derivatives according to embodiment i), wherein A represents vi) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to v), wherein R1 represents C1-4-alkylamino or N-Ci-4-alkyl-N-C1- 3-alkylamino. vii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to v), wherein R' represents C1-alkylamino. viii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to vii), wherein R3 represents C1-2-alkyl. ix) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to vii), wherein R1 represents methyl. x) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to ix), wherein R2 represents hydrogen. xi) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to ix), wherein R3 represents methoxy, and R5 and R6 represent hydrogen. xii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to ix), wherein R3 represents hydrogen, R4 represents C1-3-alkyl or methoxy, and R6 represents C1-2-alkyl or chloro. xiii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to ix), wherein R3 represents hydrogen, R4 represents methyl or ethyl, and R6 represents methyl. xiv) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to ix), wherein R3 represents hydrogen, R4 represents methoxy or methyl, and R® represents chloro. xvii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xiv), wherein R3 represents -CH2-(CH2)n- xviii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xiv), wherein R5 represents hydroxy-C25-alkoxy, di- xix) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xiv), wherein R5 represents 2,3-dihydroxy-propoxy or -OCH2-CH(0H)-CH2-NHC0R5. xx) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xviii), wherein R51 represents 2-hydroxyethyl or 2-carboxyethyl. xxi) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xviii), wherein R52 represents hydrogen. xxii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xviii), wherein R53 represents methyl or methylamino. xxiii) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xix), wherein R54 represents hydroxymethyl. xxiv) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xvii), wherein n represents the integer 1. xxv) Another embodiment of the invention relates to pyrimidine derivatives according to any one of the embodiments i) to xvi), wherein k represents the integer 1 or 2. xxvi) A further embodiment of the invention relates to pyrimidine derivatives according to embodiment i), wherein A represents wherein the asterisk indicates the bond that is linked to the pyrimidine group of formula (I); R1 represents Ci.4-alkoxy, C,.4-alkylamino, or N-Ci.4-alkyl-N-Ci-3-alkylamino; R2 represents C1-2-alkyl; R3 represents hydrogen; R3represents C1-2-alkyl; R* represents 2,3-dihydroxy-propoxy or -OCH2-CH(OH)-CH2-NHCOR^''; R'^ represents hydroxy-C,.2-alkyl; and R® represents Ci.a-alkyl. xxvii) A further embodiment of the invention relates to pyrimidine derivatives according to embodiment xxvi), wherein R^ represents Ci.4-alkylamino or N-Ci.4-alkyl-N-Ci.3-alkylamino. xxviii) A further embodiment of the invention relates to novel pyrimidine derivatives according to any one of embodiments i) to v) and viii) to xxvi), wherein R^ represents C1-4-alkoxy. xxix) A further embodiment of the invention relates to novel pyrimidine derivatives according to embodiment i), wherein A represents wherein the asterisks indicate the bond that is linked to the pyrimidine group of formula (I); R^ represents Ci.4-alkoxy, Ci.4-alkylamino, N-Ci.4-alkyl-N-Ci-3-alkylamino, C3.5-cycioalkyiamino, Css-cycloaikylmethylamino, or pyrrolidine (such as pyrro!idin-1-yl); R^ represents Ci-2-alkyi or C3.4-alkyl; R^ represents hydrogen, Ci.4-alkyl, or Ci-3-alkoxy; R" represents hydrogen, Ci.4-alkyl, or Ci-3-alkoxy; NR51R52 hydroxy-C2.5-alkoxy, di-(hydroxy-Cv4-alkyl)-Ci „-alkoxy, 2,3-dihydroxy-propoxy (such as preferably (S)-2,3-dihydroxy-propoxy), 2-hydroxy-3-methoxy-propoxy, -OCH2-(CH2)m-NR51R52, 2-[(azetidine-3-carboxylic acid)-1-yl]-ethoxy, 2-[(azetidine-3-carboxylic acid Cl 5-alkylester)-1 -yl]-ethoxy, 2-[(pyrrolidine-3-carboxylic acid)-1 -yl]-ethoxy, 2-[(pyrrolidine-3-carboxylic acid Ci.5-alkylester)-1-yl]-ethoxy, -OCH2-CH(OH)-CH2-NR51R52 3-[(azetidine-3-carboxylic acid)-1-yl]-2-hydroxypropoxy, 3-[(azetidine-3-carboxylic acid C,-5-alkylester)-1-yl]-2-hydroxypropoxy, 2-hydroxy-3-[(pyrrolidine-3-carboxyiic acid)-1 -yl]-propoxy, 2-hydroxy-3-[{pyrrolidine-3-carboxyliG acid Ci-5-alkylester)-1 -yi]-propoxy, 2-hydroxy-3-[{pyrrolidine-2-carboxylic acid)-1-yl]-propoxy, 2-hydroxy-3-[(pyrrolidine-2-carboxylic acid Ci,5-alkylester)-1-yl]-propoxy, -OCH2-(CH2)„-NHS02R53 -OCH2-CH(OH)-CH2-NHS02R53 -OCH2-(CH2)m-NHCOR54 or -OCH2-CH(OH)-CH2-NHCOR54 (wherein the carbon atom to which the hydroxy group is attached is preferably in the S-configuration); R51 represents hydrogen, Ci-3-alkyl, 2-hydroxyethyl, 2-hydroxy-1-hydroxynnethyl-ethyl, 2,3-dihydroxypropyl, 2-carboxyethyl, 2-(C(-5-alkylcarboxy)ethyl, or 2-aminoethyl; R52 represents hydrogen; R53represents C1.3-alkyl or dimethylamino; R54 represents hydroxy-Ci.2-alkyl or R55R56N-C1-2-alkyl; R55 and R56 both represent hydrogen; k and m represent the integer 1; n represents O or 1; and R® represents hydrogen, C1.4-alkyl, or halogen. xxx) Afurther embodiment of the invention relates to novel pyrimidine derivatives according to embodiment i), wherein A represents wherein the asterisk indicates the bond that is linked to the pyrimidine group of formula (I); R^ represents Ci.4-alkoxy; R2 represents C1-2-alkyl or C3.4-alkyl; R3 represents hydrogen; R4 represents C1-4-alkyl, or C1-3-alkoxy; R5 represents -(CH2)nCH(OH)-CH2-NHCOR'\ -CH2-(CH2)n-CONR''R'^ hydroxy-Cag- alkoxy, di-(hydroxy-Ci.4-alkyl)-C,.4-alkoxy, 2,3-dihydroxy-propoxy, -OCH2-(CH2)m-NR51R53 2-[(azetidine-3-carboxylic acid)-1 -yl]-ethoxy, 2-[(pyrrolidine-3-carboxylic acid)-1 -yl]-ethoxy, -0CH2-CH(0H)-CH2-NR^'R^^ 3-[(azetidine-3-carboxylic acid)-1-yl]-2-hydroxypropoxy, 2- hydroxy-3-[(pyrrolidine-3-carboxylic acid)-1 -yl]-propoxy, 2-hydroxy-3-[(pyrrolidine-2- carboxylic acid)-1-yl]-propoxy, -OCH2-CH(OH)-CH2-NHS02R53 -OCH2-(CH2)n,-NHCOR", or -OCH2-CH(OH)-CH2-NHCOR54; R51 represents hydrogen, C1-5-alkyl, 2-hydroxyethyl, 2-hydroxy-1-hydroxymethyl-ethyl, 2,3- dihydroxypropyl, carboxym ethyl, (C1-.5-alkylcarboxy)methyl, 2-carboxyethyl, 2-(Ci.5- alkylcarboxy)ethyl, or 2-aminoethyl; R52represents hydrogen, methyl, or ethyl; R53 represents Ci.3-alkyl, methylamino, ethylamino, or dimethylamino; R54 represents hydroxy-Cij-alkyl or R55R56N-Ci.2-alkyl; R^^ and R^^ independentiy represent hydrogen or methyl; m represents the Integer 1 or 2; n represents O, 1, or 2; and R* represents hydrogen, Ci.4-alkyl, or halogen. The compounds of formula (I) may contain one or more stereogenic or asymmetrie centers, such as one or more asymmetrie carbon atoms. Substituents at a doublé bond may be present in the Z- or E-configuration uniess indicated otherwise. The compounds of formula (I) may thus be present as mixtures of stereoisomers or preferably as pure stereoisomers. Mixtures of stereoisomers may be separated in a manner known to a person skilied in the art. Where the plural form is used for compounds, salts, pharmaceutical compositions, diseases and the like, this is intended to mean also a single compound, salt, or the like. Any reference hereinbefore or hereinafter to a compound of formula (I) is to be understood as referring also to salts, especially pharmaceutically acceptable salts, of a compound of formula (I), as appropriate and expediënt. Salts are preferably the pharmaceutically acceptable salts of the compounds of formula (I). The term "pharmaceutically acceptable salts" refers to non-toxic, inorganic or organic acid and/or base addition salts. Reference can be made to "Salt selection tor basic drugs", Int. J. Pharm. (1986), 33, 201-217. Examples of preferred compounds are selected from the group consisting of: N-(3-{2,6-dimethyl-4-[5-(6-methyl-2-methylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{4-[5-(2-ethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-ethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{2,6-dimethyl-4-[5-(6-methyl-2-propylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{4-[5-{2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-{3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-{3-{4-[5-(2-dimethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{4-[5-(2-{ethyl-methylamino)-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; 3-{4-[5-{2-ethylamino-6-methy(-pyrimidin-4-yl)-[1,2,4]oxadiazo(-3-yl]-2,6-dimethyl-phenoxy}- propane-1,2-diol; 3-{2,6-dimethyl-4-[5-(6-methyl-2-propylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-propane-1,2-diol; 3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; 3-{4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; 3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl-phenoxy}-propane-1,2-diol; and 3-{4-[5-(2-(ethyl-methylamino)-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl-phenoxy}-propane-1,2-diol. Examples of preferred compounds are further selected from the group consisting of: N-((S)-3-{2,6-dimethyl-4-[5-(6-methyl-2-methylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{2,6-dimethyl-4-[5-(6-methyl-2-methylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-ethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{4-[5-(2-ethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-ethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2,6-dimethyl-4-[5-(6-methyl-2-propylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{2,6-dimethyl-4-[5-(6-methyl-2-propylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-({S)-3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-(5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-{2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetannide; N-((S)-3-{4-[5-(2-dimethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxacliazol-3-yl]-2,6- climethyl-phenoxy}-2-hydroxy-propyl)-2-hyciroxy-acetamide; N-((R)-3-{4-[5-(2-dimethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-{ethyl-methylamino)-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{4-[5-(2-(ethyl-methylamino)-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dinnethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((R)-3-{4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; (S)-3-{4-[5-(2-ethylamino-6-methyl-pyrinnidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; {R)-3-{4-[5-(2-ethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; (S)-3-{2,6-dimethyl-4-[5-(6-methyl-2-propylamino-pyrimidin-4-yl)-[1,2,4]oxadiazül-3-yl]- phenoxy}-propane-1,2-diol; (R)-3-{2,6-dimethyl-4-[5-(6-methyl-2-propylamino-pyrinnidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-propane-1,2-diol; (S)-3-{4-[5-{2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl phenoxy}-propane-1,2-diol; (R)-3-{4-[5-{2-isopropyiamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yi]-2,6-dimethyl phenoxy}-propane-1,2-diol; (S)-3-{4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yi]-2,6-dimethyl- phenoxy}-propane-1,2-diol; (R)-3-{4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; (S)-3-{4-I5-{2-diethyiamino-6-methyl-pyrimidin-4-yi)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; (R)-3-{4-[5-{2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-dioi; (S)-3-{4-[5-(2-(ethyl-methylamino)-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-propane-1,2-diol; and (R)-3-{4-[5-(2-(ethyl-methylamino)-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6- dimethyl-phenoxy}-propane-1,2-diol. Further Examples of preferred compounds are selected from the group consisting of: N-(3-{2-ethyl-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadia2ol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-[3-(2-ethyl-4-{5-[2-(isobutyl-methyl-amino)-6-methyl-pyrimidin-4-yl]-[1,2,4]oxadiazol-3-yl} 6-methyl-phenoxy)-2-hydroxy-propyl]-2-hydroxy-acetamide; N-(3-{4-[5-(2-cyclopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-[3-(4-{5-[2-(cyclopropylmethyl-amino)-6-methyl-pyrimidin-4-yl]-[1,2,4]oxadiazol-3-yl}-2- ethyl-6-methyl-phenoxy)-2-hydroxy-propyl]-2-hydroxy-acetamide; N-(3-{2-ethyl-4-[5-(6-ethyl-2-ethylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{2-ethyl-6-methyl-4-[5-(2-methylamino-6-propyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetannide; N-((S)-3-{2-ethyl-4-[5-(6-isobutyl-2-methylamino-pyrimidin-4-yl)-[1,2,4]oxadia2ol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{2-ethyl-4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{2-ethyl-4-[5-(2-isobutoxy-6-methyl-pyrimidin-4-yl)-I1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{4-[5-{2-ethoxy-6-ethyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{2-ethyl-4-[5-(2-methoxy-6-propyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-nnethyl- phenoxy}-2-hydroxy-piopyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(6-isobutyl-2-methoxy-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-(3-{2-chloro-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; 2-hydroxy-N-(2-hydroxy-3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)- [1,2,4]oxadiazol-3-yl]-2-methoxy-6-methyl-phenoxy}-propyl)-acetamide; N-(3-{2-chloro-4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; 3-{2-ethyl-4-[5-{2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-propane-1,2-diol; 3-{2-ethyl-4-[5-(2-isobutylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-propane-1,2-diol; 3-{4-[5-(2-cyclopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6-methyl-phenoxy}-propane-1,2-ciiol; 3-{2-ethyl-4-[5-(6-ethyl-2-ethylamino-pyrimiclin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenoxy}-propane-1,2-diol; 3-{2-ethyl-4-[5-(6-ethyl-2-ethylamino-pyr(midin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenoxy}-propane-1,2-diol; 3-{2-ethyl-4-[5-(6-isobutyl-2-methoxy-pyrimidin-4-yl)-[1,2,4]oxadia2ol-3-yl]-6-methyl-phenoxy}-propane-1,2-diol; 3-{4-[5-(6-ethyl-2-ethylamino-pyrimidin-4-yl)-[1,2,4]oxadia2ol-3-yl]-2,6-dimethyl-phenoxy}-propane-1,2-diol; 3-{4-[5-(6-ethyl-2-ethylamino-pyrimidln-4-yl)-[1,2,4]oxadia2ol-3-yl]-2,6-dimethyl-phenoxy}-propane-1,2-diol; 3-{2-chloro-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenoxy}-propane-1,2-diol; 3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-methoxy-6-methyl-phenoxy}-propane-1,2-diol; 3-{2-chloro-4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenoxy}-propane-1,2-diol; N-((S)-3-{2-ethyl-4-[3-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-5-yl]-6-methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; 3-(3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6-methyl-phenoxy}-2-hydroxy-propylamino)-propionic acid; and 3-{2-ethyl-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl-phenyl}-N-(2-hydroxy-ethyi)-propionamide. Further Examples of preferred compounds are further selected from the group consisting of: N-({S)-3-{2-ethyl-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-[(S)-3-(2-ethyl-4-{5-[2-(isobutyl-methyl-amino)-6-methyl-pyrimidin-4-yl]-[1,2,4]oxadiazol- 3-yl}-6-methyl-phenoxy)-2-hydroxy-propyl]-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-cyclopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yi]-2-ethyl-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-[(S)-3-(4-{5-[2-(cyclopropylmethyl-amino)-6-methyl-pyrimidin-4-yl]-[1,2,4]oxadiazol-3-yi}- 2-ethyl-6-methyl-phenoxy)-2-hydroxy-propyl]-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(6-ethyl-2-ethylamino-pyrirnidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-6-methyi-4-[5-(2-methylamino-6-propyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3- yl]-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(6-isobutyl-2-methylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-isobutoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{4-[5-(2-ethoxy-6-ethyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(2-methoxy-6-propyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-ethyl-4-[5-(6-isobutyl-2-methoxy-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; N-((S)-3-{2-chloro-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadtazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; 2-hydroxy-N-((S)-2-hydroxy-3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)- [1,2,4]oxadiazol-3-yl]-2-methoxy-6-methyl-phenoxy}-propyl)-acetamide; N-((S)-3-{2-chloro-4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; (S)-3-{2-ethyl-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-propane-1,2-diol; (S)-3-{2-ethyl-4-[5-(2-isobutylamino-6-methyl-pyrinnidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-propane-1,2-diol; (S)-3-{4-[5-{2-cyclopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6- methyl-phenoxy}-propane-1,2-diol; (S)-3-{2-ethyl-4-[5-(6-ethyl-2-ethylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-propane-1,2-diol; (R)-3-{2-ethyl-4-[5-(6-ethyl-2-ethylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-propane-1,2-diol; (S)-3-{2-ethyl-4-[5-(6-isobutyl-2-methoxy-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-propane-1,2-diol; (S)-3-{4-[5-(6-ethyl-2-ethylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; (R)-3-{4-[5-(6-ethyl-2-ethylamino-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2,6-dimethyl- phenoxy}-propane-1,2-diol; (S)-3-{2-chloro-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6- methyl-phenoxy}-propane-1,2-diol; (S)-3-{4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-methoxy-6- methyl-phenoxy}-propane-1,2-diol; (S)-3-{2-chloro-4-[5-(2-isopropoxy-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenoxy}-propane-1,2-diol; N-((S)-3-{2-ethyl-4-[3-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-5-yl]-6- methyl-phenoxy}-2-hydroxy-propyl)-2-hydroxy-acetamide; 3-((S)-3-{4-[5-(2-diethylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-2-ethyl-6- methyl-phenoxy}-2-hydroxy-propylamino)-propionic acid; and 3-{2-ethyl-4-[5-(2-isopropylamino-6-methyl-pyrimidin-4-yl)-[1,2,4]oxadiazol-3-yl]-6-methyl- phenyl}-N-(2-hydroxy-ethyl)-propionamide. The compounds of formula (I) and their pharmaceutically acceptable salts, can be used as a medicament, e.g. in the form of pharmaceutical compositions for enteral or parenteral administration, and are suitable for decreasing the number of circulating lymphocytes and for the prevention and/or treatment of diseases or disorders associated with an activated immune system. The production of the pharmaceutical compositions can be effected in a manner which will be familiar to any person skilled in the art (see for example Remington, The Science and Practice of Pharmacy, 21 st Edition (2005), Part 5, "Pharmaceutical Manufacturing" [published by Lippincott Williams & Wilkins]) by bringing the described compounds of formula (I) or their pharmaceutically acceptable salts, optionally in combination with other therapeutically valuable substances, into a galenical administration form together with suitable, non-toxic, inert, pharmaceutically acceptable solid or liquid carrier materials and, if desired, usual pharmaceutical adjuvants. Diseases or disorders associated with an activated immune system which can be treated and/or prevented with the compounds of formula (I) inciude rejection of transpianted organs, tissue or cells; graft-versus-host diseases brought about by transplantation; autoimmune syndromes including rheumatoid arthritis; systemic lupus erythematosus; antiphospholipid syndrome; Hashimoto's thyroiditis; lymphocytic thyroiditis; multiple sclerosis; myasthenia gravis; type I diabetes; uveitis; episcleritis; scleritis; Kawasaki's disease, uveo-retinitis; posterior uveitis; uveitis associated with Behcet's disease; uveomeningitis syndrome; allergie encephalomyelitis; chronic allograft vasculopathy; post-infectious autoimmune diseases including rheumatic fever and post-infectious glomerulonephritis; inflammatory and hyperproliferative skin diseases; psoriasis; psoriatic arthritis; atopic dermatitis; myopathy; myositis; osteomyelitis; contact dermatitis; eczematous dermatitis; seborrhoeic dermatitis; lichen planus; pemphigus; bullous pemphigoid; epidermolysis bullosa; urticaria; angioedema; vasculitis; erythema; cutaneous eosinophilia; acne; scleroderma; alopecia areata; keratoconjunctivitis; vernal conjunctivitis; keratitis; herpetic keratitis; dystrophia epithelialis corneae; corneal leukoma; ocular pemphigus; Mooren's ulcer; ulcerative keratitis; scleritis; Graves' ophthalmopathy; Vogt-Koyanagi-Harada syndrome; sarcoidosis; pollen allergies; reversible obstructive airway disease; bronchial asthma; allergie asthma; intrinsic asthma; extrinsie asthma; dust asthma; chronic or inveterate asthma; late asthma and airway hyper-responsiveness; bronehiolitis; bronchitis; endometriosis; orchitis; gastric ulcers; isehemie bowei diseases; inflammatory bowel diseases; necrotizing enterocolitis; intestinal lesions associated with thermal burns; coeliac disease; proctitis; eosinophilic gastroenteritis; mastocytosis; Crohn's disease; ulcerative colitis; vascular damage caused by isehemie diseases and thrombosis; atherosclerosis; fatty heart; myocarditis; cardiac infaretion; aortitis syndrome; cachexia due to viral disease; vascular thrombosis; migraine; rhinitis; eczema; interstitial nephritis; IgA-induced nephropathy; Goodpasture's syndrome; hemolytic-uremic syndrome; diabetic nephropathy; glomerulosclerosis; glomerulonephritis; tubulointerstitial nephritis; interstitial cystitis; multiple myositis; Guillain-Barré syndrome; Meniere's disease; polyneuritis; multiple neuritis; myelitis; mononeuritis; radiculopathy; hyperthyroidism; Basedow's disease; thyrotoxieosis; pure red eell aplasia; aplastic anemia; hypoplastic anemia; idiopathic thrombocytopenic purpura; autoimmune hemolytic anemia; autoimmune thrombocytopenia; agranulocytosis; pernicious anemia; megaloblastic anemia; anerythroplasia; osteoporosis; fibroid lung; idiopathic interstitial pneumonia; dermatomyositis; leukoderma vulgaris; ichthyosis vulgaris; photoallergic sensitivity; cutaneous T cell lymphoma; polyarteritis nodosa; Huntington's chorea; Sydenham's chorea; myoeardosis; myocarditis; scleroderma; Wegener's granuloma; Sjogren's syndrome; adiposis; eosinophilic fascitis; lesions of gingiva, periodontium, alveolar bone, substantia ossea dentis; male pattern alopecia or alopecia senilis; muscular dystrophy; pyoderma; Sezary's syndrome; hypophysitis; chronic adrenal insufficiency; Addison's disease; ischemia-reperfusion injury of organs which occurs upon preservation; endotoxin shock; pseudomembranous colitis; colitis caused by drug or radiation; isehemie acute renal insufficiency; chronic renal insufficiency; lung caneer; malignancy of lymphoid origin; acute or chronic lymphocytic leukemias; lymphoma; pulmonary emphysema; cataracta; siderosis; retinitis pigmentosa; senile macular degeneration; vitreal scarring; corneal alkali burn; dermatitis erythema; ballous dermatitis; cement dermatitis; gingivitis; periodontitis; sepsis; pancreatitis; peripheral artery disease; carcinogenesis; solid cancer tumors; metastasis of carcinoma; hypobaropathy; autoimmune hepatitis; primary biliary cirrhosis; sclerosing cholangitis; partial liver resection; acute liver necrosis; cirrhosis; alcoholic cirrhosis; hepatic failure; fulminant hepatic failure; late-onset hepatic failure; and "acute-on-chronic" liver failure. Preferred diseases or disorders to be treated and/or prevented with the compounds of formula (I) are selected from the group consisting of rejection of transplanted organs such as kidney, liver, heart, lung, pancreas, cornea, anó skin; graft-versus-host diseases brougbt about by stem cell transplantation; autoimmune syndromes including rheumatoid arthritis, multiple sclerosis, inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, psoriasis, psoriatic arthritis, thyroiditis such as Hashimoto's thyroiditis, uveo-retinitis; atopic diseases such as rhinitis, conjunctivitis, dermatitis; asthma; type I diabetes; post-infectious autoimmune diseases including rheumatic fever and post-infectious glomerulonephritis; solid cancers and tumor metastasis. Particuiarly preferred diseases or disorders to be treated and/or prevented with the compounds of formula (1) are selected from the group consisting of rejection of transplanted organs selected from kidney, liver, heart and lung; graft-versus-host diseases brought about by stem cell transplantation; autoimmune syndromes selected from rheumatoid arthritis, multiple sclerosis, psoriasis, psoriatic arthritis, Crohn's disease, and Hashimoto's thyroiditis; and atopic dermatitis. Very preferably the diseases or disorders to be treated and/or prevented with the compounds of formula (I) are selected from multiple sclerosis and psoriasis. The present invention also relates to a method for the prevention or treatment of a disease or disorder mentioned herein comprising administering to a subject a pharmaceutically active amount of a compound of formula (I). Furthermore, compounds of the formula (1) are also useful in combination with one or several immunomodulating agents for the prevention and/or treatment of the diseases and disorders mentioned herein. According to a preferred embodiment of the invention, said agents are selected from the group consisting of immunosuppressants, corticosteroids, NSAID's, cytotoxic drugs, adhesion molecule inhibitors, cytokines, cytokine inhibitors, cytokine receptor antagonists and recombinant cytokine receptors. The present invention also relates to the use of a compound of formula (I) for the preparation of a pharmaceutical composition, optionally for use in combination with one or several immunomodulating agents, for the prevention or treatment of the diseases and disorders mentioned herein. The compounds of formula (I) can be manufactured by the methods given below, by the methods given in the Examples or by analogous methods. Optimum reaction conditions may vary with the particular reactants or solvents used, but such conditions can be determined by a person skilled in the art by routine optimisation procedures. Compounds of the formula (I) of the present invention can be prepared according to the genera! sequence of reactions outlined below. Only a few of the synthetic possibilities ieading to compounds of formula (I) are described. Structure 1 Compounds of formula (I) which represent a 5-pyrimidin-4-yl-[1,2,4]oxadiazole derivative, are prepared by reacting a compound of Structure 1 in a solvent such as dioxane, THF, dimethoxyethane, xylene, toluene, benzene, pyridine, DMF, dichloromethane, acetic acid, trifluoroacetic acid, etc. at rt or elevated temperatures in the presence or absence of auxiliaries such as acids (e.g. TFA, acetic acid, HCI, etc), bases (e.g. NaH, NaOAc, Na2C03, K2CO3, triethylamine, etc), tetraalkylammonium salts, or water removing agents (e.g. oxalyl chloride, a carboxylic acid anhydride, POCI3, PCI5, P4O10, molecular sieves, methoxycarbonylsulfamoyl triethylammonium hydroxide (Burgess reagent), etc.) (Lit.: e.g. A. R. Gangloff, J. Litvak, E. J. Shelton, D. Sperandio, V. R. Wang, K. D. Rice, Tetrahedron Lett. 42 (2001), 1441-1443; T. Suzuki, K. Iwaoka, N. Imanishi, Y. Nagakura, K. Miyta, H. Nakahara, M. Ohta, T. Mase, Chem. Pharm. Buil. 47 (1999), 120-122; R. F. Poulain, A. L. Tartar, B. P. Déprez, Tetrahedron Lett. 42 (2001), 1495-1498; R. M. Srivastava, F. J. S. Oliveira, D. S. Machado, R. M. Souto-Maior, Synthetic Commun. 29 (1999), 1437-1450; E. o. John, J. M. Shreeve, Inorganic Chemistry 27 (1988), 3100-3104; B. Kaboudin, K. Navaee, Heterocycles 60 (2003), 2287-2292). Compounds of Structure 1 may be prepared by reacting a compound of Structure 2 with a compound of Structure 3 in a solvent such as DMF, THF, DCM, etc. in the presence or absence of one or more coupling agents such as TBTU, DCC, EDC, HBTU, HOBt, CDI, PyBOP, etc. and in the presence or absence of a base such as triethylamine, DIPEA, NaH, K2CO3, etc. (Lit.: e.g. A. Hamze, J.-F. Hernandez, P. Fulcrand, J. Martinez, J. Org. Chem. 68 (2003) 7316-7321; and the literature cited above). Compounds of formula (I) which represent a 3-pyrimidin-4-yi-[1,2,4]oxadiazole derivative are prepared in an analogous fashion (Lit.: e.g. C. T. Brain, J. M. Paul, Y. Loong, P. J. Oakley, Tetrahedron Lelt. 40 (1999) 3275-3278) by reacting a compound of Structure 4 with a compound of Structure 5 and subsequent cyclisation of the corresponding hydroxyamidine ester intermediate. Compounds of Structure 5 are either commercially available or are prepared according to procedures described herein or according to procedures known to a person skilled in the art. Compounds of Structure 3 and 4 may be prepared by reacting a compound of Structure 6 and 7, respectively, with hydroxylamine or one of its salts in a solvent such as metfianol, ethanol, pyridine, etc. in the presence or absence of a base such as NaaCOs, KaCOa, triethyiamine, KOtBu, etc. (Lit.: e.g. T. Suzui