Chymopapain-Catalyzed Direct Asymmetric Aldol Reaction

Chymopapain, a cysteine proteinase isolated from the latex of the unripe fruits of Carica papaya, displays a promiscuous activity to catalyze the direct asymmetric aldol reactions of aromatic and heteroaromatic aldehydes with cyclic and acyclic ketones in acetonitrile in the presence of a phosphate buffer. The excellent enantioselectivities of up to 96% ee and high diastereoselectivities of up to >99:1 (anti/syn) were achieved. The novel catalytic promiscuity of chymopapain widens the applicability of this biocatalyst in organic synthesis.