Enzymatic Basis of Stereochemical Control in Reserpine Biosynthesis

Reserpine is a landmark natural product that has profoundly influenced our understanding of neurotransmitter biology and cardiovascular medicine. Its complex structure, featuring a unique C3 β-configuration and five consecutive chiral centers, has inspired generations of synthetic chemists to develop innovative strategies for its construction. However, the biosynthetic logic underlying nature's stereochemical control in the assembly of this intricate molecule has remained elusive. Here, we investigate the biosynthetic pathway of reserpine in Rauvolfia verticillata, revealing that α-configured strictosidine serves as the biosynthetic precursor. The crucial C3 β-configuration is established through a two-step enzymatic epimerization, orchestrated by a flavin-dependent oxidase and a NADPH-dependent reductase. The consecutive chiral centers are constructed through coordinated action of distinct enzyme families. Through the identification of eight biosynthetic enzymes, including those catalyzing late-stage methoxylation, we successfully reconstituted the biosynthesis of rauvomitorine G, which contains all the stereochemical features present in reserpine. This work unveils nature's elegant approach to stereoselective synthesis of complex alkaloids and provides valuable biocatalytic tools for molecular functionalization.