DESC:Technical field of Invention:
The present invention relates to synthesis of N-heterocyclic N-alkyl piperazine N-oxide derivatives for use in the treatment of type-2 diabetes mellitus (T2DM). More specifically, the invention relates to synthesis of N-oxide derivatives of Blonanserin, Clozapine, and Olanzapine. The present invention also provides a process for the preparation of various N-oxide salts and cocrystals to modulate the solubility of N-heterocyclic N-alkyl piperazine N-oxide molecules with pharmaceutically acceptable coformers, such as benzoic acid, barbituric acid, oxalic acid, malonic acid, maleic acid, salicylic acid, nicotinic acid, fumaric acid, phthalic acid, terephthalic acid, benzenesulfonic acid, methanesulfonic acid, hydrochloric acid. The invention furthermore relates to methods of lowering blood glucose levels in type 2 diabetes mellitus using N-heterocyclic N-alkyl piperazine N-oxide derivatives or its salts or its crystals thereof.

Background of the Invention:
Blonanserin (BLN) is an antipsychotic agent, having dopamine D2 and serotonin 5-HT2A receptor antagonist properties. Similarly Olanzapine (OLN) and Clozapine (CLN) also belong to the category of SNRI drugs (serotonin norepinephrine reuptake inhibitors used for treatment schizophrenia). Diabetes is a metabolic condition where the tissues in the body fail to absorb the sugars from the ingested food, resulting in increased sugar concentration in the blood stream. Failure to control the blood sugar has serious life threatening consequences such as heart disease, blindness, renal disorder. Diabetes mellitus can be either Type-I (T1DM, caused by genetic aberration) or Type-II (T2DM, insufficient release of insulin). In the later form of the diabetes, the patient is either insulin resistant or has relatively minimal insulin. The one challenge is how to make a T2DM patient more insulin sensitive. The other is how to increase endogenous insulin levels in T2DM patients. One way to address the problem is to target the pancreatic ß–cells for increasing endogenous insulin levels. The first-line treatment for type 2 diabetes is diet, weight control and physical activity and if blood sugar (glucose) level remains high despite the lifestyle changes then the patients will be put under anti-diabetic drugs or on insulin.

There is a lot of literature on anti-diabetic drugs that can be used for the treatment of type-2 diabetes such as metformin; sulfonylureas such as gliclazide, glimepiride, (C. J. Dunn, D. H. Peters, Drugs, 1995, 49, 721–49.; D. B. Campbell, R. Lavielle, C. Nathan, Diabetes Res. Clin. Pr., 1991, 14, S21-S36.; S. N. Davis, J. Diabetes Complicat., 2004, 18, 367-376), and glipizide; Nateglinide and repaglinide (P. Venkatesh, T. Harisudhan, H. Choudhury, R. Mullangi, N. R. Srinivas, Biomed. Chromatogr., 2006, 20, 1043–1048.; E. S. Horton, C. Clinkingbeard, M. Gatlin, J. A. M. E. S. Foley, S. U. S. A. N. Mallows, S. H. A. R. O. N. Shen, Diabetes Care, 2000, 23, 1660–1665.; D. R. Owens, Diabetic Medicine, 1998, 15, S28–S36.); Dipeptidyl peptidase 4 inhibitors (also known as incretin enhancers) such as linagliptin, saxagliptin, sitagliptin and vildagliptin (A. J. Scheen, Expert Opin. Drug Metab. Toxicol., 2011, 7, 1561-1576.; P. Aschner, M. S. Kipnes, J. K. Lunceford, M. Sanchez, C. Mickel, D. E. Williams-Herman, Diabetes Care, 2006, 29, 2632-2637.; B. O. Ahrén, M. Landin-Olsson, P. A. Jansson, M. Svensson, D. Holmes, Schweizer, A. J. Clin. Endocrinol. Metab., 2004, 89, 2078-2084.); Thiazolidinediones such as pioglitazone; (A. J. Scheen, Diabetes Res. Clin. Pr., 2012, 98, 175-186.;); glucagon-like peptide-1 mimetics such as exenatide and liraglutide (O. G. Kolterman, D. D. Kim, L. Shen, J. A. Ruggles, L. L. Nielsen, M. S. Fineman, Baron, A. D. Am. J. Health Syst. Pharm., 2005, 62, 173-181.; M. Nauck, A. Frid, K. Hermansen, N. S. Shah, T. Tankova, I. H. Mitha, M. Zdravkovic, M. Düring, D. R. Matthews, Diabetes Care, 2009, 32, 84-90).

Many of the above drugs have terrific side effects such as Hypoglycaemia; bloating, wind, and diarrhoea; feeling sick and headaches, etc. Therefore, there remains a need in the art for newer drugs with fewer side effects for the treatment of complex disease such as diabetes. To fulfil the above need, the present inventors have explored the efficacy of N-alkyl N-heterocyclic piperazine N-oxide derivatives of formula I as non-insulin anti-diabetic drugs.

Object of the invention:
Therefore, the main objective of this invention is to synthesize N-heterocyclic N-alkyl piperazine N-oxide of formula I to explore its efficacy in type-2 diabetes mellitus (T2DM).

Another objective of the invention is to improve the solubility and crystallinity of N-heterocyclic N-alkyl piperazine N-oxide of formula I by preparing co-crystals and salts with different GRAS acids/amides and also with some inorganic acids.

Summary of the invention:
In accordance with the above objectives, the invention provides a process for synthesis of N-heterocyclic N-alkyl piperazine N-oxide of formula I, to explore the efficacy in the treatment of type-2 diabetes (T2DM).

N-heterocyclic N-alkyl piperazine N-oxide of formula I
Accordingly, the invention encompasses the synthesis of N-oxide of the general structure I where R1 = methyl, ethyl, n-alkyl, branched alkyl; Ring1 = phenyl, substituted phenyl, thienyl, cyclohexyl, cyclooctyl; X = N-R, C-R where R = H, phenyl, substituted phenyl; and Y = CH, C=C, CH=CH, phenyl, substituted phenyl, thienyl. The said invention is exemplified through the N-oxide compounds of Blonanserin, Olanzapine and Clozapine as depicted in Scheme 1. Furthermore the N-oxides of general formula I are shown to have utility in treatment of type-2 diabetes mellitus (T2DM).
Scheme 1

In yet another aspect, the present invention provides a process for the preparation of the above N-oxides in pure form. The solubility of the N-oxides derivatives prepared according to the invention was found to be low. Therefore, in another aspect, the invention provides co-crystals and salts of N-oxides derivatives to improve the solubility of the same. Thus, the present invention also provides preparation of cocrystals with GRAS conformers (Table1) such as benzoic acid, barbituric acid, oxalic acid, malonic acid, maleic acid, salicylic acid, nicotinic acid, fumaric acid, phthalic acid and terephthalic acid to improve solubility.

In another aspect, the present invention also provides preparation of pharmaceutical salts of N-oxides with GRAS molecules such as benzenesulfonic acid, methanesulfonic acid, hydrochloric acid to improve solubility. In a further aspect, the present invention provides structural confirmation of the formation of N-oxide at the piperazine N atom from the X-ray crystal structure of Blonanserin N-oxide dihydrate, and Blonanserin N-oxide–oxalic acid cocrystals. Furthermore the cocrystals and salts were characterised by IR, NMR, DSC, and PXRD.

In yet another aspect, the invention also discloses the solubility studies of Blonanserin N-oxide and Blonanserin N-oxide–maleic acid cocrystal in water, with cocrystal aqueous solubility of 14.18 mg/mL, a value that is 15 times higher than that of pure Blonanserin N-oxide (0.943 mg/mL).

In accordance with the above objective, the investigation of in vivo antidiabetic activity of Blonanserin N-oxide, Clozapine N-oxide which was carried out in STZ streptozotocin induced Wistar rats and comparison was made between N-oxides of BLN and CLN with known antidiabetic drugs such as Metformin and Sitagliptin.

In another aspect, the investigation of the hypoglycemic effect of BLN-O and CLN-O and on comparison with standard marketed drugs metformin and sitagliptinin normal control and orally glucose-induced hyperglycaemic Wistar rats, which proves that the investigated drugs, BLN-O and CLN-O are comparable with metformin and sitagliptin thereby providing new drugs for the treatment of type-2 diabetes mellitus (T2DM).

Therefore, in yet another aspect, the invention provides methods of treating type-2 diabetes in a subject which method comprises administering therapeutically effective amount of N-oxides derivatives of formula I to the subject in need thereof.

In yet another object, the invention provides compounds of N-oxides derivatives of formula I, for use in treatment of type-2 diabetes mellitus (T2DM) in a subject.

Brief description of the drawings:
Figure 1 depicts 1HNMR (in CDCl3) of Blonanserin N-oxide.
Figure 2 Shows the comparison of 1HNMR (in CDCl3) spectra ofBlonanserin and Blonanserin N-oxide. The downfield shift of the ethyl group protons indicates oxidation to N-oxide at the outer piperazine N.
Figure 3 depicts FT-IR spectra of Blonanserin N-oxide.
Figure 4 depicts the DSC thermogram of Blonanserin N-oxide.
Figure 5 depicts HRMS of Blonanserin N-oxide which shows that single peak at m/z = 384 [M+1] which is a characteristic molecular ion peak of Blonanserin-N-oxide (367 + 16 = 383).
Figure 6 depicts PXRD lines of Blonanserin N-oxide.
Figure 7 depicts the 1HNMR of Clozapine N-oxide.
Figure 8 shows the FT-IR spectra of Clozapine N-oxide.
Figure 9 depicts the 1HNMR of Olanzapine N-oxide.
Figure 10 shows the FT-IR spectra of Olanzapine N-oxide.
Figure 11 depicts PXRD line pattern of BLN-O and BZA cocrystal (benzoic acid) with its starting components. The cocrystal exhibits unique line pattern compared to the starting materials.
Figure 12 depicts the overlay of PXRD line pattern of BLN-O and BTA cocrystal (barbituric acid) with its individual components.
Figure 13 depicts the overlay of PXRD pattern of BLN-O and OA cocrystal (oxalic acid) with its individual components.
Figure 14 depicts the overlay of PXRD pattern of BLN-O and MA cocrystal (malonic acid) with its individual components.
Figure 15 depicts the overlay of PXRD pattern of BLN-O and MLA cocrystal (maleic acid) with its individual components.
Figure 16 depicts the overlay of PXRD pattern of BLN-O-SLA cocrystal (salicylic acid) with its individual components.
Figure 17 depicts the overlay of PXRD pattern of BLN-O-NIC cocrystal with its individual components.
Figure 18 depicts the overlay of PXRD pattern of BLN-O and FA cocrystal (fumaric acid) with its individual components.
Figure 19 depicts the overlay of PXRD pattern of BLN-O and PTA cocrystal (phthalic acid) with its individual components.
Figure 20 depicts the overlay of PXRD pattern of BLN-O and TPTA cocrystal (terephthalic acid) with its individual components.
Figure 21 depicts (a) ORTEP diagram of BLN-O dihydrate and (b) tetramer unit formed by four water and BLN-oxide molecules.
Figure 22 depicts (a) ORTEP diagram of BLN-oxide–OA and (b) BLN-oxide molecules flanked on both sides of the channel formed by oxalic acid.
Figure 23 depicts the overlay of PXRD pattern of BLN-O and besylate salt (benzenesulfonate) with pure BLN-oxide.
Figure 24 Comparison of FT-IR spectra of BLN-O and besylate salt (benzenesulfonate) with its individual components.
Figure 25 DSC thermograms of BLN-O and BLN-O besylate salt.
Figure 26 Comparison of 1HNMR spectra for BLN-O and BLN-O besylate salt.
Figure 27 PXRD comparison of BLN-mesylate salt (methanesulfonate) with pure BLN-O.
Figure 28 FT-IR comparison of BLN-O (green) and BLN-O-mesylate salt (red)
Figure 29 PXRD comparison of BLN-O with BLN-O-hydrochloride salt.
Figure 30 FT-IR comparison of BLN-O with BLN-O-hydrochloride salt.
Figure 31 DSC thermograms of BLN-O and BLN-O-hydrochloride salt.
Figure 32 depicts the 28 study results of 1X dosage of BLN-O and CLNO on STZ treated rats with drug administered daily at 1mg/kg dose.
Figure 33 depicts the 18 day study results of 5X dosage experiments of BLN-O and CLN-O on STZ treated rats with drug administered daily 5mg/kg dose and compared with standard marketed forms Metformin HCl (MHCL) and Sitagliptin phosphate monohydrate (SPMH). The control group CNTRL was not treated with STZ.
Figure 34 Shows the comparison of test drugs N-oxides of CLN and BLN (at 5 mg/kg, oral) with the standard drugs Metformin HCl and Sitagliptin phosphate monohydrate (100 mg/kg, i.p.) on glucose induced hyperglycemic OGTT (oral glucose tolerance test)

Abbreviations used in the patent specification are provided in below table.
Table 1
Barbituric acid, BTA
Benzenesulfonic acid, BSA
Benzoic acid, BZA
Blonanserin N-oxide, BLN-O
Clozapine N-oxide, CLN-O
Fumaric acid, FA
Generally Regarded As Safe, GRAS
Hydrochloric acid, HCl
Intraperitoneally, IP
Maleic acid, MLA Malonic acid, MA
Methanesulfonic acid, MSA
Nicotinic acid, NIC
Olanzapine N-oxide, OLN-O
Oral glucose tolerance test, OGTT
Oxalic acid, OA
Phthalic acid, PTA
Powder X-ray diffraction, PXRD
Salicylic acid, SLA
Streptozotocin, STZ
Terephthalic acid, TPTA

Detailed Description of the Invention:
The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

Accordingly, the invention provides a process for synthesis of N-heterocyclic N-alkyl piperazine N-oxide of formula I, which comprises;
R1 = methyl, ethyl, n-alkyl, branched alkyl; Ring1 = phenyl, substituted phenyl, thienyl, cyclolhexyl, cyclooctyl; X = N-R, C-R where R = H, phenyl, substituted phenyl; and Y = CH, C=C, CH=CH, phenyl, substituted phenyl, thienyl.

N-heterocyclic N-alkyl piperazine N-oxide of formula I
The compounds of formula I are prepared by:
a) Reacting N-heterocyclic N-alkyl piperazine of formula II with an oxidizing agent in a solvent.
b) Isolating N-heterocyclic N-alkyl piperazine N-oxide of formula I.

The oxidizing agent is selected form 30% to 50% H2O2, m-CPBA, urea-H2O2, etc.
The reaction may be conducted from 0 °C temperature to reflux temperature of the solvent.

The solvent may be selected from dichloromethane, dichloroethane, C1 to C4 alcohols or any suitable inert solvents for the smooth functioning of the reaction.
The N-heterocyclic N-alkyl piperazine of formula II is exemplified from a group consisting of Blonanserin, Clozapine and Olanzapine.

N-heterocyclic N-alkyl piperazine of formula II

In structure II, R1 = methyl, ethyl, n-alkyl, branched alkyl; Ring1 = phenyl, substituted phenyl, thienyl, cyclolhexyl, cyclooctyl; X = N-R, C-R where R = H, phenyl, substituted phenyl; and Y = CH, C=C, CH=CH, phenyl, substituted phenyl, thienyl.

Accordingly, the invention encompasses the synthesis of N-oxide metabolites of the Blonanserin, Olanzapine and Clozapine as depicted in scheme 1 for use in the treatment of type-2 diabetes mellitus (T2DM),
Scheme 1

In another embodiment, the present invention provides a process for the preparation of the N-oxides in pure form as described below.

Blonanserin was dissolved in methanol and stirred at room temperature until it dissolved completely. To this reaction mixture, 30% H2O2 was added and refluxed at 70 °C for 2 h. After completion of the reaction, methanol was removed by rotary evaporator resulting in a viscous liquid. The reaction mixture was then extracted with CHCl3 and H2O. The CHCl3 layer was treated with Na2SO4 to remove excess H2O and then evaporated on rotary evaporator. On evaporating CHCl3, sticky solid was obtained, which was stirred with pentane to obtain white colour solid, which was further dried on vacuum pump for 2 h. Formation of Blonanserin N-oxide was characterised by 1HNMR, FT-IR, HRMS, DSC and PXRD (Figure 1-6).

In another embodiment, N-oxide of clozapine was prepared by dissolving clozapine in dichloromethane and kept at 0°C for 5 min. To the cool solution, m-CPBA solution in CH2Cl2 was added drop wise at 0 °C. After the completion of the reaction monitored by TLC, NaHCO3 solution was added and stirred for 10 min. The reaction mixture was then extracted with CHCl3 and H2O. The CHCl3 layer was treated with Na2SO4 to remove excess H2O and then evaporated on rotary evaporator. On evaporation a light yellow colour solid was obtained which was further dried on vacuum pump for 2h. The resultant material was characterised by 1HNMR, FT-IR and PXRD (Figure 7-8).
Similarly in a further embodiment, Olanzapine was dissolved in dichloromethane and kept at 0 °C for 5 min. To the cool solution, m-CPBA (0.085 g, 2.4 mmol) solution in CH2Cl2 was added drop wise at 0 °C. After the completion of reaction, monitored by TLC, NaHCO3 solution was added and stirred for 10 min. The reaction mixture was then extracted with CHCl3 and H2O. The CHCl3 layer was treated with Na2SO4 to remove excess H2O and then evaporated on rotary evaporator. On evaporation a light yellow colour solid was obtained which was further dried on vacuum pump for 2 h. The compound was then purified by column chromatography (ethyl acetate: methanol 7:3 v/v). Powder material was analysed by 1HNMR and FT-IR (Figure 9-10).

In another aspect, as the solubility was found to be low for the N-oxide derivatives, the present invention provides N-oxide cocrystals with GRAS conformers (Table 1) such as benzoic acid, barbituric acid, oxalic acid, malonic acid, maleic acid, salicylic acid, nicotinic acid, fumaric acid, phthalic acid and terephthalic acid to improve solubility.

In another aspect, the present invention also provides preparation of pharmaceutical salts of N-oxides with GRAS molecules such as benzenesulfonic acid, methanesulfonic acid, hydrochloric acid to improve solubility.

In a further aspect, the present invention also provides structural confirmation of the formation of N-oxide at the piperazine N atom from the X-ray crystal structure of Blonanserin N-oxide dihydrate, and Blonanserin N-oxide–oxalic acid cocrystal. Furthermore, the cocrystals and salts were characterised by IR, NMR, DSC, and PXRD.

In yet another embodiment, the invention also discloses the solubility studies on Blonanserin N-oxide and Blonanserin N-oxide–maleic acid cocrystal in water, with cocrystal aqueous solubility of 14.18 mg/mL, a value that is 15 times higher that of pure Blonanserin N-oxide (0.943 mg/mL).
In a further embodiment, the investigation of in vivo antidiabetic activity of Blonanserin N-oxide, Clozapine N-oxide which was carried out in STZ streptozotocin induced Wistar rats and compared the hypoglycemic effect of N-oxides of BLN and CLN with known antidiabetic drugs such as Metformin and Sitagliptinon normal control and orally glucose-induced hyperglycaemic Wistar rats. According to this experiment, the immediate control of glucose levels (4 h) as well as those in long term study of 28 days with test drugs is comparable to standard drugs. The results from the animal study indicate that N-oxides of Antipsychotic drugs are useful compounds to lower blood glucose levels in type 2 diabetes patients.

Therefore, in yet another embodiment, the invention provides methods of lowering blood glucose levels in type-2 diabetes (T2DM) patients which method comprises administering therapeutically effective amount of N-oxides derivatives of formula I or its cocrystals or salts thereof optionally in association with one or more pharmaceutical excipients. The therapeutically effective amount is an amount that renders the patient disease free. The therapeutically effective amount normally ranges from 2.5 mg to 20 mg once or twice a day.

In yet another embodiment, the invention provides compounds of N-oxide derivatives of formula I or its cocrystals or salts thereof, for use in lowering blood glucose levels and the treatment of type-2 diabetes mellitus (T2DM) in a subject.

In yet another embodiment, the invention provides use of N-oxide derivatives of formula I, or its cocrystals or salts thereof for preparation of medicament useful for lowering the blood glucose levels in type-2 diabetes (T2DM) in a subject.

In a further embodiment, the invention provides pharmaceutical compositions comprising N-oxide derivatives of formula I or its cocrystals or salts thereof in association with one or more pharmaceutical carriers or excipients, for lowering blood glucose levels in type-2 diabetes mellitus (T2DM).
The pharmaceutical composition may be prepared as per conventional methods using conventional excipients and in conventional dosage forms.

Pharmaceutical compositions of the present invention suitable for oral administration may be prepared as discrete units such as capsules, cachets, or tablets, each containing a predetermined amount of the active ingredient, in the form of a powder or granules, tablets, capsules or as a solution or a suspension in an aqueous liquid, a non-aqueous liquid, an oil-in-water emulsion, or a water-in-oil liquid emulsion. Such compositions may be prepared by any of the methods known in the art. However, the preparation methods include the step of bringing into association the active ingredient with one or more pharmaceutical carriers by uniformly and intimately admixing the active ingredient with finely divided solid carriers or with liquid carriers and shaping the product into the desired presentation such as tablets, pellets, capsule, granules, syrups, suspensions, solutions and the like.

The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the invention.

Examples
Example 1
(a) Preparation of N-oxide of Blonanserin
Blonanserin (200 mg, 0.54 mmol) was dissolved in 15 mL of methanol and stirred at room temperature until it dissolved completely. To this reaction mixture 1.44 mL of 30% H2O2 was added and refluxed at 70 °C for 2 h. After completion of the reaction (by TLC), methanol was removed by rotary evaporator resulting in a viscous liquid. The reaction mixture was then extracted with CHCl3 and H2O. The CHCl3 layer was treated with Na2SO4 to remove excess H2O and then evaporated on rotary evaporator. After evaporation of volatiles, a white solid was obtained which was further dried on vacuum pump for 2 h. Formation of Blonanserin N-oxide was characterised by 1HNMR, FT-IR, HRMS, DSC and PXRD (Figure 1-6).

Scheme 2 Schematic representation of formation of BLN-O from blonanserin

Reaction time: 2 h (on TLC there was no starting left)
Work up: Extraction with CHCl3 and H2O. On evaporating CHCl3, sticky solid was obtained. Pentane was added to the sticky solid and the product was stirred for 1 h in pentane and filtered. A white colour solid was obtained.
M.p.: 143-145 °C
Yield: 140 mg (yield 67%). In multiple batches yield is 70-75%.
1H NMR (CDCl3, 400 MHz): 7.22 (t, 2 H, J 12 Hz), 7.10 (t, 2H, 12 Hz), 6.37 (s, 1 H), 4.13 (d, 2 H, 10.8 Hz), 3.82 (t, 2 H, J 20 Hz), 3.43-3.30 (m, 6 H), 2.90 (t, 2 H, 8Hz), 2.60 (t, 2 H, J 8 Hz), 1.79 (s, 2 H), 1.49-1.36 (m, 10 H).

(b) Preparation of N-oxide of Clozapine
Clozapine (0.2 g, 0.61 mmol) was dissolved in 4 mL of dichloromethane and kept at 0°C for 5 min. To the cool solution, m-CPBA (0.18 g, 1.15 mmol) solution in CH2Cl2was added drop wise at 0 °C. After 1 h, reaction was monitored by TLC and found that reaction completed. To the reaction mixture, NaHCO3 solution was added and stirred for 10 min. The reaction mixture was then extracted with CHCl3 and H2O. The CHCl3 layer was treated with Na2SO4 to remove excess H2O and then evaporated on rotary evaporator. On evaporation a light yellow colour solid was obtained which was further dried on vacuum pump for 2h. The resultant material was characterised by 1HNMR, FT-IR and PXRD (Figure 7-8).
Reaction time: 1 h
Yield: 160 mg.80%

Scheme 3 Schematic representation of the formation of CLN-O from clozapine.

(c) Preparation of N-oxide of Olanzapine
Olanzapine (0.1 g, 0.32 mmol) was dissolved in 4 mL of dichloromethane and kept at 0 °C for 5 min. To the cool solution, m-CPBA (0.085 g, 2.4 mmol) solution in CH2Cl2 was added drop wise at 0 °C. After 1 h, reaction was monitored by TLC and found that reaction completed. To the reaction mixture, NaHCO3 solution was added and stirred for 10 min. The reaction mixture was then extracted with CHCl3 and H2O. The CHCl3 layer was treated with Na2SO4 to remove excess H2O and then evaporated on rotary evaporator. On evaporation a light yellow colour solid was obtained which was further dried on vacuum pump for 2h. The compound was then purified by column chromatography (ethyl acetate: methanol 7:3 v/v). Powder material was analysed by 1HNMR and FT-IR (Figure 9-10).
Yield: 50 mg, 50%,
Reaction time: 1 h
M.p.: 214 °C

Scheme 4 Schematic representation of the formation of OLN-O from olanzapine.

Example 2
Crystal structure description
BLN-O dihydrate: The compound (BLN-O) was subjected to crystallization experiments in various solvent combinations to get suitable crystals for X-ray analysis. Single crystal of BLN-O was attempted in several solvent systems but diffraction quality crystals were obtained in DMSO: H2O (1:1 v/v) mixture. The crystal structure was solved and refined in Pbca space group with one molecule of BLN–O and two water molecules in the asymmetric unit. From the crystal structure analysis the oxidation took place at the expected position of the piperazine N atom of the Blonanserin with the N–O bond length of 1.38 Å. The compound crystallized as a dihydrate. The ORTEP diagram of Blonanserin N-oxide dihydrate confirms oxidation at the expected position of piperizine N-oxide (Figure 21).
BLN-O-Oxalic Acid Cocrystal: About 30 mg of ground material of BLN-O and Oxalic acid was crystallized in chloroform (6 mL) solvent, which resulted in single crystals suitable for X-ray diffraction after 2-3 days. Crystal structure was solved and refined in Pbca space group with one molecule of BLN-O and Oxalic acid in the asymmetric unit. In the crystal structure oxalic acid forms a channel along b-axis and BLN-O molecules are flanked on both sides of the channel. Hydrogen atoms were omitted for clarity (Figure 22).

Example 3
Preparation of cocrystals
BLNO-Benzoic Acid (1:1): Blonanserin N-oxide and Benzoic acid were ground in 1:1 stoichiometric ratio of BLNO (100 mg) and Benzoic Acid (31.8 mg) in a mortar and pestle for 1 h by adding catalytic amount of acetonitrile and the resultant material was analysed by PXRD.
BLNO-Barbituric Acid (1:1): Blonanserin N-oxide (100 mg) and Barbituric acid (33.4 mg) ground together in a mortar and pestle for 30-40 min using few drops of acetonitrile solvent and the resulting material was analysed by PXRD.
BLNO-Oxalic Acid (1:1): Stoichiometric amount of Blonanserin N-oxide (100 mg) and Oxalic acid (23.4 mg)were ground in 1:1 stoichiometric ratio in a mortar and pestle for 1 h by adding catalytic amount of solvent. The ground material was analyzed by PXRD.
BLNO-Malonic Acid (1:1): Blonanserin N-oxide (100 mg) and Malonic acid (32.1 mg)were ground in 1:1 stoichiometric ratio in a mortar and pestle for 1 h using acetonitrile as solvent and powder material obtained was analysed by PXRD.
BLNO-Maleic Acid (1:1): Blonanserin N-oxide (100 mg) and Maleic acid (30.3 mg) were ground in 1:1 stoichiometric ratio for 1 h using acetonitrile as solvent and the resulting material was analysed by PXRD.
BLNO-Salicylic Acid (1:1): Blonanserin N-oxide (100 mg) and Salicylic acid (36.0 mg) were ground in 1:1 stoichiometric ratio for 1 h using acetonitrile as solvent and the resulting material was analysed by PXRD.
BLNO-Nicotinic Acid (1:1): Blonanserin N-oxide (100 mg) and nicotinic acid (36.0 mg) were ground in 1:1 stoichiometric ratio for 1 h using acetonitrile as solvent and the resulting material was analysed by PXRD.
BLNO-Fumaric Acid (1:1): Blonanserin N-oxide (100 mg) and maleic acid (30.1 mg) were ground in 1:1 stoichiometric ratio for 1 h using acetonitrile as solvent and the resulting material was analysed by PXRD.
BLNO-Phthalic Acid (1:1): Blonanserin N-oxide (100 mg) and phthalic acid (43.3 mg) were ground in 1:1 stoichiometric ratio for 1 h using acetonitrile as solvent and the resulting material was analysed by PXRD.
BLNO-Terephthalic Acid (1:1): Blonanserin N-oxide (100 mg) and terephthalic acid (43.3 mg) were ground in 1:1 stoichiometric ratio for 1 h using acetonitrile as solvent and the resulting material was analysed by PXRD.

Example 4
Preparation of Salts
BLNO-Besylate Salt (1:1): Blonanserin N-oxide-besylate salt was obtained by slurry crystallization technique. To the stoichiometric ratio of Blonanserin N-oxide (200 mg) in diisopropyl ether (10 mL), benzene sulfonic acid (78.8 mg) dissolved in methanol (8 mL) was added and a clear solution was observed. After stirring this clear solution for overnight powder material was obtained. The powder thus obtained was filtered and dried in oven and the material was analysed through FT-IR, NMR, and DSC.
BLN-O-Mesylate Salt (1:1): Blonanserin N-oxide-besylate salt was obtained in slurry crystallization technique. To the stoichiometric ratio of Blonanserin N-oxide (200 mg) in diisopropyl ether, methanesulfonic acid (50µL, 50 mg) which was dissolved in methanol was added and clear solution was observed. After stirring this clear solution for overnight powder material was obtained. The powder thus obtained was filtered and dried in oven and the material was analysed through FT-IR, NMR, and DSC.
BLN-O-Hydrochloride salt (1:1) Blonanserin N-oxide (150 mg) and 1 mL of HCl(35%) in methanol was added in a 25 mL round bottom flask. Clear solution was obtained which on stirring for overnight gave powder. The powder thus obtained was filtered and dried in oven and the material was analysed through FT-IR, NMR, and DSC.
Example 5
Solubility study of BLN-O and BLN-O-MLA (maleic acid cocrystal):
Equilibrium solubility experiments were carried out in water medium for 24h. Initially, calibration curve was obtained for Blonanserin N-oxide, and BLN-O-MLA by plotting absorbance vs. concentration for known concentration solutions in water medium. BLN-O showed two peaks (?max) in UV-Vis spectra at 233 nm and 308 nm. The maximum absorbance was at 233 nm and also there was no interference of maleic acid hence we considered 233 nm for calculation. The slope of the plot from the standard curve gave the molar extinction coefficients (e) 17.018 mL mg–1 cm–1 for Blonanserin N-oxide (BLN-O) and 22.764 mL mg–1 cm–1 for BLN-O-MLA. The solubility of the Blonanserin N-oxide was found to be 0.943 mg/mL whereas BLN-O-MLA is 14.180 mg/mL (about 15 times higher). The PXRD of the left material after equilibrium solubility experiment showed the stability of the Blonanserin N-oxide and BLN-O-MLA in the experimental conditions.

Example 6
To assess the antidiabitic activity, the rats were subjected to overnight on fasting, diabetes condition was induced with a single intraperitoneal injection (i.p.) of Streptozotocin (STZ) at a dose of 40 mg/kg. The STZ was freshly dissolved in citrate buffer (0.01M, pH 4.5).23 The injection volume was 1.0 mL/kg. The animals were fed 5% of glucose solution to overcome drug induced hypoglycaemia. The experimental animals were allowed to drink 5% glucose solution to overcome the drug induced hypoglycemia. After 3 days of standard STZ induction, blood glucose levels were measured and the animals with a glucose concentration of more than 300 mg/dL were classified as diabetic and taken for the experiment. Administration of the BLN-O, CLN-O was started on 4th day after STZ injection and this was considered to be the 1st day of treatment, which was continued for 28 days for 1X dosage and 18 days for 5X dosage.

Effect of BLNO and CLNO in STZ induced rats
After noting the insulinogenic activity of novel antidiabetic compounds CLNO and BLNO, we tested these N-oxides in Wistar rats. First the pancreas of animals was impaired by dosing with streptozotocin (STZ) at 40 mg/kg. The rats were divided into 5 groups:
Group 1: Positive control rats were administered STZ but no drug (diabetic rats)
Group 2: Male diabetic rats received BLNO at 1 mg/kg dose (intraperitoneal, i.p.)
Group 3: Male diabetic rats received CLNO at 1 mg/kg dose (i.p.)
Group 4: Female diabetic rats received BLNO at 1 mg/kg dose (i.p.)
Group 5: Female diabetic rats received CLNO at 1mg/kg dose (i.p.)

1X dose study:
Fasting blood glucose level and body weight were measured at 1st, 3rd, 6th, 9th, 12th, 15th, 18th, 21st, 24th, and 27th day. The pancreas of rats was impaired by STZ treatment (40 mg/kg) and then study was started after 3 days. Blood samples were obtained by pricking the tail vein. The N-oxides of antipyschotic drugs BLNO and CLNO showed positive results at 1 mg/kg dosage. Plasma glucose values decreased significantly (P < 0.0001) from about ˜ 380 mg/dL to 90 mg/dL at the end of 28 days, while for the control group (STZ induced group, no drug) the value increased to 550-600 mg/dL (Figure 32; values are listed in Table 2). The dramatic increase in glucose levels in the control group was due to their impaired pancreas by STZ.

Table 2 Effect of BLNO on blood glucose level of STZ induced diabetic Wistar rats.
Groupa Blood Glucose level (mg/dL)b
Initial day 1st day 3rd day 6th day 9th day 12th day 15th day 18th day 21st day 24th day 27th day
I (Control) 95 ± 8.4 425 ± 32.6 524 ±18.5 538 ± 19.2 551 ±17.9 565 ±16.6 570 ±25.4 585 ± 34.7 588 ± 19.6 593 ±14.4 595 ± 14.7
II (Male rats BLNO) 97 ± 4.3 384 ± 30.5 341 ± 16.7 290 ± 15.1 240 ± 17.8 191 ± 7.3 146 ± 6.4 108 ± 9.5 94 ± 4.6 95 ± 6.8 92 ± 4.7
III (Male rats CLNO) 91 ± 5.3 376 ± 15.6 319 ± 18.8 268 ± 7.4 209 ± 15.7 165 ± 4.6 131 ± 8.5 99 ± 5.2 94 ± 8.4 93 ± 7.8 88 ± 4.6
IV (Female rats BLNO) 96 ± 3.3 375 ± 32.6 340 ± 23.7 291 ± 16.4 280 ± 13.8 189 ± 14.9 149 ± 7.4 111 ± 5.7 97 ± 9.8 94 ± 2.6 90 ± 3.5
V (Female rats CLNO) 99 ± 7.4 385 ± 19.1 321 ± 16.6 269 ± 4.8 210 ± 13.9 162 ± 5.6 127 ± 9.9 89 ± 8.3 93 ± 4.8 92 ± 3.6 90 ± 5.7

a Groups are defined in Experimental section.
b The mean difference is significant at 0.0001 level (P test).

Example 7
In screening 5X dosage toxicity white male and female wistar rats having an average body weight of 200-250g were taken. The animals were kept fasting for overnight providing only water, after which the N-oxides of psychotic drugs BLN-O and CLN-O were administrated (i.p) to four groups each consisting of 6 rats. If mortality was observed in 4 out of 6 animals per group, then the dose administered was assigned as toxic dose. Body weight before and after administration were noted and behavior pattern were observed and also sign of tremors, convulsions, salivation, diarrhea, lethargy, sleep and coma were seen. Treatment with 5 mg/kg of BLNO and CLNO showed significant decrease in plasma glucose values, much faster than the 1X dose study. The plasma glucose levels dropped significantly from ˜ 390 mg/dl to 90 mg/dl at the end of 9th day (Table 3 and Figure 33). The onset of toxicity and signs of side effects were not observed. The N-oxides of BLN-O and CLN-O found to be safe at dose of 5 mg/kg body weight of Wistar rat.

Table 3 Effect of BLNO and CLNO on blood glucose level of STZ induced diabetic Wistar rats.
Groupa Blood Glucose level (mg/dL)b
Initial day 1st day 3rd day 6th day 9th day 12th day 15thday 18thday
I (Control) 94 ± 13.6 98 ± 8.9 96 ± 5.4 91 ± 7.8 86 ± 9.6 93 ± 6.4 99 ± 9.1 92 ± 3.5
II (Male rats BLNO) 96 ± 8.7 379 ± 27.8 306 ± 29.4 213 ± 34.6 127 ± 18.8 89 ± 9.7 92 ± 9.3 92 ± 6.8
III (Male rats CLNO) 97 ± 4.6 385 ± 34.7 302 ± 24.6 212 ± 18.8 117 ± 13.6 87 ± 8.4 92 ± 9.1 94 ± 7.2
IV (Female rats BLNO) 92 ± 7.5 391 ± 38.5 311 ± 25.6 216 ± 36.8 128 ± 13.9 87 ± 9.6 90 ± 11.9 92 ± 7.4
V (Female rats CLNO) 95 ± 3.8 386 ± 23.4 301 ± 22.5 214 ± 19.6 122 ± 14.8 91 ± 11.9 90 ± 8.4 95 ± 9.3

a Groups are defined in Experimental section.
b The mean difference is significant at 0.0001 level (P test).

Example 8
Oral glucose tolerance test (OGTT) for non-diabetic rats were performed according to the standard method (M. A Islam, M. A. Akhtar, M. R. Khan, M. S. Hossain, A. H. Alam, M. I. Ibne-Wahed, MD Shah Amran, M. Ahmed, Pak. J. Pharm. Sci, 2009, 22, 402–404). In short, Group I to Group V was selected for OGT test after starving at water for 16 hours. The baseline glucose level was measured by glucometer to the glucose fed (3 g/kg body weight) rats. Group I stands for normal control group. Group II is treated with sitagliptin (100 mg/kg body weight). Group III and IV was treated with the N-oxides of Blonanserin and Clozapine administered intraperitoneally (IP) to the glucose fed (3 g/kg body weight) rats at the dose of 5 mg/kg body weight. And Group V is treated with Metformin (100mg/kg) to the glucose fed (3 g/kg body weight) rats. Serum glucose of blood sample from tail vein was estimated by using glucometer at 0, 15, 30, 45, 60, 90 and 120 min. Data were expressed as mean (Table 4 and Figure 34). Experimental induction of hyperglycemia by intragastric ingestion of glucose resulted in two-fold increase in plasma glucose levels. There was a significant (P <0.05) reduction of glucose levels by the test drugs BLN-O and CLN-O. OGTT tests confirm the results of STZ induced rats by an independent model of investigation to induce high glucose levels at the start of the experiment. The immediate control of glucose levels (4 h) as well as those in long term study of 28 days with test drugs is comparable to standard drugs. The results from our animal study indicate that N-oxides of Antipsychotic drug promising candidates to lower blood glucose levels in type 2 diabetes patients.

Table 4 Effect of BLNO and CLNO on blood glucose level on OGTT Wistar rats
Groupa Blood Glucose level (mg/dL)b
0 min 15 min 30 min 45 min 60 min 90 min 120 min
I (Control) 89 ± 6.3 209 ± 5.1 180 ±5.5 130 ± 5.3 118 ± 7.8 105 ± 4.1 98 ± 6.3
II (MHCL 100 mpk) 93 ± 4.8 112 ± 3.5 157 ± 6.5 132 ± 4.4 112 ± 5.5 104 ± 6.1 90 ± 4.9
III (SPMH 100 mpk) 91 ± 5.7 182 ± 7 117 ± 4.2 112 ± 6.2 131 ± 5.1 102 ± 4.3 90 ± 5
IV (BLNO 5 mpk) 88 ± 9.6 117 ± 7 139 ± 8 156 ± 5.6 140 ± 6 115 ± 7.5 106 ± 8.1
V (CLNO 5 mpk) 91 ± 4.9 135 ± 5.3 157 ± 5.8 120 ± 6.5 103 ± 7.5 102 ± 5.3 90 ± 9.9

a Groups are defined in Experimental section.
b The mean difference is significant at the 0.05 level (P test).

Example 9
(a) Powder X-ray Diffraction (PXRD)
Powder X-ray diffraction technique is a standard method used for the characterization of solid-state forms. Therefore the technique of PXRD is vital and predominant tool for the study of polycrystalline materials, and is eminently suited for the routine characterization and to know the phase changes of solid material. PXRDs were recorded on SMART Bruker D8 Focus Powder X-ray diffractometer using Cu-Ka radiation (? = 1.5406 Å) at 40 kV and 30 mA. All the pure N-oxides of blonanserin, clozapine and olanzapine, and also the cocrystals and salts were characterised by PXRD. Appearance or disappearance of powder lines with respect starting components was taken into consideration to characterise the solid forms (Figure 11-20).
(b) Single crystal X-ray diffraction
Good quality single crystals of BLN–O dihydrate obtained from the DMSO: H2O (1:1 v/v) mixture and for BLN–O-oxalic acid co-crystal were mounted on the goniometer of Bruker SMART CCD diffractometer equipped with Mo-Ka radiation (? = 0.71073 Å) source. Data reduction was performed using Bruker SAINT software. Intensities were corrected for absorption using SADABS, and the structures were solved and refined using SHELX-97. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms on hetero atoms were located from difference electron density maps and all C-H hydrogens were fixed geometrically.
(c) Thermal analysis
Differential Scanning Calorimetry (DSC) was used for the thermal analysis BLN–O, BLN–O-besylate salt and BLN–O-hydrochloride salt. DSC was performed on a Mettler Toledo DSC 822e module by placing 4-5 mg of samples in aluminium pans and the temperature range is 30-200 °C at a heating rate of 5 °C min–1. BLN–O exhibits endotherm at 152°C accompanied by immediate decomposition exotherm at 160 °C, whereas BLN–O-hydrochloride salt shows similar behaviour with lower decomposition exotherm at 141 °C, and for BLN–O-besylate salt complete melting endotherm can be seen at 98 °C (Figure 4, 25 and 31). ,CLAIMS:1. A process for synthesis of N-heterocyclic N-alkyl piperazine N-oxide of formula I, which comprises;

N-heterocyclic N-alkyl piperazine N-oxide of formula I
Wherein R1 = methyl, ethyl, n-alkyl, branched alkyl; Ring1 = phenyl, substituted phenyl, thienyl, cyclohexyl, cyclooctyl; X = N-R, C-R where R = H, phenyl, substituted phenyl; and Y = CH, C=C, CH=CH, phenyl, substituted phenyl, thienyl.
a) Reacting N-heterocyclic N-alkyl piperazine of formula II with 30% to 50% H2O2 or m-CPBA or urea-H2O2 in a solvent and
b) Isolating N-heterocyclic N-alkyl piperazine N-oxide of formula I in pure form.

N-heterocyclic N-alkyl piperazine of formula II
2. The process according to claim 1, wherein, N-heterocyclic N-alkyl piperazine of formula II is selected from the group consisting of Blonanserin, Clozapine and Olanzapine.
3. The process according to claim 1, wherein, the N-heterocyclic N-alkyl piperazine N-oxide of formula I comprises

4. Cocrystal compounds or salts of N-heterocyclic N-alkyl piperazine N-oxide of formula I with improved solubility, comprises N-heterocyclic N-alkyl piperazine N-oxide of formula I and a coformers.
5. The cocrystal compounds of N-heterocyclic N-alkyl piperazine N-oxide of formula I according to claim 4, wherein, a) the coformer is selected from the group consisting of benzoic acid, barbituric acid, oxalic acid, malonic acid, maleic acid, salicylic acid, nicotinic acid, fumaric acid, phthalic acid or terephthalic acid and b) the N-heterocyclic N-alkyl piperazine N-oxide of formula I is selected from the group consisting of N-oxides of Blonanserin, Clozapine and Olanzapine.
6. The cocrystal salts of N-heterocyclic N-alkyl piperazine N-oxide of formula I with improved solubility according to claim 4, wherein, a) the coformer is selected from the group consisting of benzenesulfonic acid, methanesulfonic acid, and hydrochloric acid and b) the N-heterocyclic N-alkyl piperazine N-oxide of formula I is selected from the group consisting of N-oxides of Blonanserin, Clozapine and Olanzapine.
7. A method of lowering blood glucose levels in type-2 diabetes patients which method comprises administering therapeutically effective amount of N-oxides derivatives of formula I or its cocrystals or salts thereof in association with one or more pharmaceutical excipients.
8. The method according to claim 7, wherein, the therapeutically effective amount ranges from 2.5 mg to 20 mg and the subject is human.
9. N-oxide derivatives of formula I or its cocrystals or salts thereof, for use in lowering blood glucose levels in type-2 diabetes mellitus (T2DM) patients.
10. Pharmaceutical compositions comprising N-oxide derivatives of formula I or its cocrystals or salts thereof in association with one or more pharmaceutical excipients or carriers, for use in lowering blood glucose levels in type-2 diabetes mellitus (T2DM) patients.