Chemoenzymatic Total Synthesis of (+)-Galanthamine and (+)-Narwedine from Phenethyl Acetate.

Abstract

The stereoselective total synthesis of unnatural (+)-galanthamine starting from phenethyl acetate is described. Chirality was introduced via microbial dihydroxylation of phenethyl acetate with the recombinant strain JM109 (pDTG601A) to the corresponding cis-cyclohexadi-enediol, configuration of which provided the absolute stereochemistry of the ring C of (+)-galanthamine. Intramolecular Heck cyclization was used to form the quaternary carbon and dibenzofuran functionality. The synthesis of (+)-galanthamine was completed in a total of ten steps and an overall yield of 5.5 %. Experimental and spectral data are provided for all new compounds.