[Natural products syntheses based on the biotransformation using biocatalyst]

This review summarizes the chemoenzymatic synthesis of the biologically active natural products based on a combination of chemical diastereoselectivity and enzymatic enantioselectivity using biocatalyst. Asymmetric reduction of 2-methyl-3-keto ester with yeast gave the optically active syn-2-methyl-3-hydroxy ester, which was converted to natural product such as (-)-oudemansin B. Asymmetric hydrolysis of 3-acetoxy-2-methy esters possessing syn- or anti-structure afforded the optically active 3-hydroxy-2-methyl esters and 3-acetoxy-2-methy esters corresponding to the starting material. One of these optically active 3-hydroxy-2-methyl esters was converted to aglycone of macrolide, venturicidins A and B possessing 10 chiral centers. Both primary alcohols possessing a chiral center at β-position of hydroxyl group and secondary alcohols were subjected to the lipase-assisted acylation in the presence of acyl donor to afford the optically active esters and the optically active alcohols corresponding to the starting material. These optically active compounds were converted to the biologically active natural products such as bisabolane type sesquiterpenes, decaline type diterpenes or triterpenes, nikkomycin B, (+)-asperlin, (-)-chuangxinmycin, (-)-indolmycin, cystothiazoles melithiazols, myxothiazols and piericidins possessing antifungal and cytotoxicic activities, inhibition of NADH oxidation, etc. Reaction of primary alcohol and glucose using immobilized β-glucosidase gave alkyl β-glucosides in high yield. Pentaacetate of allyl β-glucoside was subjected to Mizoroki-Heck type reaction with phenylboronic acid derivatives to give phenylpropenoid β-D-glucopyranosid congeners.