Stereoselective Synthesis of Benzylated Prodelphinidins and Their Diastereomers with Use of the Mitsunobu Reaction in the Preparation of Their Gallocatechin Precursors

✍ Scribed by Karsten Krohn; Ishtiaq Ahmed; Markus John; Matthias C. Letzel; Dietmar Kuck

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 620 KB
• Volume: 2010
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.201000053

✦ Synopsis

Abstract

The tetrabenzylated catechin 9 was prepared by benzylation of the commercially available pure (+)‐catechin (3) and coupled with the commercially unavailable pentabenzylated(–)‐gallocatechin 10, prepared in a one‐step Mitsunobu‐type cyclization of the triol 8. The highly stereoselective synthesis of benzylated prodelphinidins – catechin‐(4α→8)‐gallocatechin (13), gallocatechin‐(4α→8)‐gallocatechin (14), and gallocatechin‐(4α→8)‐catechin (15) – is reported for the first time. The ESI(+)‐CID mass spectra of the coupling products were found to feature regioselective retro‐Diels–Alder (RDA) reactions and unusual sequential losses of pairs of C~7~H~7~^·^ radicals (182 u) from the Na^+^ adduct ions.