We Claim:-1. A compound of formula (I) or a pharmaceutically acceptable salt or solvate thereof:
wherein
R is selected from halogen, aryl, alkyl-aryl, heteroaryl, heteroaryl-alkyl, heterocyclyl and heterocyclyl-alkyl which is optionally further substituted with 1-3 halogen atoms, C1-C6 alkoxy, straight or branched C1-C6 alkyl, straight or branched C2-C6 alkenyl;
2. The compound as claimed in claim 1, wherein R is selected from aryl, aryl-alkyl, heteroaryl, heterocyclyl, preferably phenyl, benzyl, naphthyl, tolyl, xylyl, biphenyl, anthracene, pyridazinyl, pyridinyl, pyrimidinyl, quinolinyl, pyrrolyl, pyrazolyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, thiadiazolyl, isothiazolyl, furyl, thienyl, oxadiazolyl, pyrazinyl, more preferably phenyl and thienyl.
3. The compound as claimed in claim 1, wherein the compound of formula (II) is:

or a pharmaceutically acceptable salt thereof or a solvate thereof.
4. The compound as claimed in claim 1, wherein compound of formula (III) is:
or a pharmaceutically acceptable salt thereof or a solvate thereof. 5. The compound of claim 1 is selected from the group consisting of:

(i) Reacting a compound of Formula (A) with substituted carbonyl
chloride in presence of a base to form a residue.
(ii) Residue of step (i) was washed and extracted with an organic
solvent to obtain a solid;
(iii) The solid obtained in step (ii) was re-crystallized from organic
solvent and purified.
7. A pharmaceutical composition comprising a therapeutically effective amount of the compound or a pharmaceutically acceptable salt or solvate thereof as claimed in any one of claims 1-5 as an effective ingredient and a pharmaceutically acceptable carrier.
8. A pharmaceutical composition as claimed in claim 7 for use in the prevention or treatment of Dengue virus infections by inhibiting dengue virus protease.