Syntheses relevant to vitamin B12 biosynthesis: the malate route to (–)-ring-B imide and synthesis of the 2,7,20-trimethylisobacteriochlorin
Abstract
An efficient enantioselective synthesis of (–)-ring-B imide (19) from R-malic acid is outlined and this product is used for synthesis, by a photochemical route, of the 2,7,20-trimethylisobacteriochlorin (3), of importance for biosynthetic research on vitamin B12.