| 主权项 |
1. A process for total synthesis of flavonoid compound of formula I and isomers thereof,wherein R1 and R2 is OH; R3═H, orthe process comprising the steps of:
i. protecting the hydroxyl groups of phloroglucinol and hydroxyl groups of caffeic acid as ethers by using a protecting group and a base in a solvent to get 1,3,5-tris(methoxymethoxy) benzene (5) and (E)-methyl3-(3,4-dihydroxyphenyl) acrylate (6) respectively; where MOMO is methoxymethoxy and OMOM is also methoxymethoxy; ii. hydrolyzing of the (E)-methyl 3-(3,4-dihydroxyphenyl)acrylate (6) obtained in step (i) by using a hydrolyzing agent to get (E)-3-(3,4-bis(methoxymethoxy) phenyl)acrylic acid (7); iii. acylating the 1,3,5-tris(methoxymethoxy)benzene (5) and (E)-3-(3,4-bis (methoxymethoxy) phenyl)acrylic acid (7) obtained in steps (i & ii) in presence of an acylating agent in a solvent at a temperature ranging between −5° C. to 0° C. to get (E)-3-(3,4-bis(methoxymethoxy)phenyl)-1-(2,4,6-tris(methoxymethoxy)phenyl) prop-2-en-1-one (8); iv. oxidizing (E)-3-(3,4-bis(methoxymethoxy)phenyl)-1-(2,4,6-tris(methoxymethoxy) phenyl)prop-2-en-1-one (8) obtained in step (iii) with an oxidizing agent to get racemic epoxide((3-(3,4-bis(methoxymethoxy)phenyl)oxiran-2-yl)(2,4,6-tris(methoxymethoxy)phenyl) methanone) (9); v. reacting the epoxide compound ((3-(3,4-bis(methoxymethoxy)phenyl)oxiran-2-yl)(2,4,6-tris (methoxymethoxy) phenyl)methanone) (9) obtained in step (iv) by using excess of acid in different ratio of mixture of solvent ranging in the ratio of 0:1/1:0 to 5:1/1:5 to obtain racemic taxifolin 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxychroman-4-one(+/−Taxifolin) (10); vi. optionally separating the racemic taxifolin 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxychroman-4-one(+/−Taxifolin) by chromatographic method to obtain (−) taxifolin and (+) taxifolin (11) and (12); and vii. refluxing the racemic or (+)taxifolin or (−)taxifolin obtained in steps (v) and (vi) in a solvent and D-glucose in presence of a Lewis acid at a temperature ranging between 85° C. to 90° C. for a period ranging between 24 h to 48 hr to get diastereomeric mixture of taxifolin-glucopyranosides or (2R,3R)-Taxifolin-6-C-beta-D-Glucopyranoside or Ulmoside A respectively; separating the diastereomeric mixture of taxifolin-glucopyranosides to obtain (2R,3R) taxifolin-6-C-β-D-glucopyranoside (2) and (2S,3S) taxifolin-6-C-β-D-glucopyranoside (ulmoside A) pure product |
