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■ Total Synthesis of Racemic Physostigmine, Physovenine and Its Sulfur Analogue by the Oxindole-5-O-tetrahydropyranyl Ether Route

Qian-sheng Yu, Bao-yuan Lu, and Xue-Feng Pei*

*Department of Chemistry, Georgetown University, Washington DC 20057, USA

Abstract

1,3-Dimethyl-5-tetrahydropyranyloxyoxindole (4) was synthesized from 4-methylaminophenol sulfate (metol) (1). Phase transfer catalyzed C3-alkylation of compound (4) produced alcohol (5), nitrile (8), and thioalcohol (13) after treatment of bromide (12) with thiourea. Compound (5) and (13) were converted into racemic physovenine (7) and thiaphysovenine (15) by reaction with LAH, in situ deprotection, and reaction of phenols with methyl isocyanate. Conversion of nitrile (8) into racemic physostigmine (11) which included a reductive N-methylation of 9 was similarly accomplished.