Stereochemistry of the Cyclization-Rearrangement of (+)-Copalyl Diphosphate to (-)-Abietadiene Catalyzed by Recombinant Abietadiene Synthase from Abies grandis

摘要

Syntheses and enzymatic cyclizations of 8α-hydroxy-17-nor copalyl diphosphate (8α), (15R)-[15-~2H_1] 8b, and (15R,17E)-[15-~3H_1,17-~2H_1] copalyl diphosphate ([~2H,~3H] 2) catalyzed by recombinant abietadiene synthase (rAS) gave 17-nor manoyl oxide (9a), (16E)-[16-~2H_1] 9b, and (15S,16R)-[16-~2H_1,16-~3H_1] abietadiene ([~2H_1,~3H_1] 4), respectively. These and other results indicate that conversion of CPP (2) to abietadiene (4) occurs by anti S'_N cyclization to a sandaracopimar-15-en-8-yl carbocation intermediate (13~+, 13β-methyl) followed by hydrogen transfer and methyl migration suprafacially on the si face of the vinyl group.