The invention discloses a compound of formula (I) wherein, at least one of R1, R2, R3 and R4 is —C(═O)Rn and R1, R2R3 and R4 are H or CH3 and Rn is alkyl or alkenyl group. The alkenyl group have one or more number of double bonds either in cis form or trans form or both. In Rn, where n is 12 to 30 carbons; and pharmaceutically acceptable salt thereof. The said alkenyl groups are preferably selected from the group consisting of eicosapentaenoic acid (EPA) or DHA (docosahexaenoic acid). This invention further discloses processes for their preparation of compounds of formula I and pharmaceutical compositions that contain these compounds.