Procyanidin B-2

原花青素B2Chemical Name: (2R,2'R,3R,3'R,4R)-2,2'-Bis(3,4-dihydroxyphenyl)-3,3',4,4'-tetrahydro-2H,2'H-4,8'-bi-1-benzopyran-3,3',5,5',7,7'-hexaol
CAS No. 29106-49-8
项目整合开发状态: Phase II
项目研究机构: Kyowa Hakko (Originator)
合成路线:The oxidation of 5,7-bis(benzyloxy)-2(R)-[3,4-bis(benzyloxyphenyl]-3,4-dihydro-2H-1-benzopyran-3(S)-ol with Dess Martin periodinane (DMP) in dichloromethane gives the corresponding ketone (II),which is reduced with L-Selectride in THF yielding the 5,7-bis(benzyloxy)-2(R)-[3,4-bis(benzyloxyphenyl]-3,4-dihydro-2H-1-benzopyran-3(R)-ol (III).The oxidation of (III) with DDQ in presence of ethylene glycol affords the 2-hydroxyethoxy derivative (IV),which is condensed with (III) by means of titanium tetrachloride in THF/dichloromethane yielding the dihydroxylated dimer (V).The esterification of both hydroxyls of (V) with 3,4,5-tris(benzyloxy)benzoyl chloride (VI) by means of DMAP in pyridine affords the fully protected target compound (VII),which is finally debenzylated by hydrogenolysis with H2 over Pd/C in methanol/water.

合成路线:Protection of (+)-catechin (I) with benzyl bromide gives the tetra-O-benzylcatechin (II).Epimerization of (II) in then accomplished by oxidation to ketone (III),using the Dess-Martin periodinane reagent,followed by ketone reduction with L-selectride to furnish the tetra-O-benzyl epicatechin (IV).Oxidation of (IV) with DDQ in the presence of ethyleneglycol gives rise to the 4-(hydroxyethoxy) derivative (V).Subsequent coupling between tetra-O-benzyl epicatechin (IV) and the 4-(hydroxyethoxy) derivative (V) in the presence of TiCl4 produces a mixture of epicatechin oligomers,from which the desired benzyl-protected dimeric compound (VI) is isolated by column chromatography.Finally,deprotection of the octa-benzyl ether (VI) is effected by hydrogenolysis in the presence of Pd/C.