Reductive Thioalkylation of a Kalafungin Analogue

Abstract

Reduction of pyranonaphthoquinone 3 with sodium dithionite in the presence of the sulfur nucleophiles thiocresol, benzylmercaptan and butanethiol afforded the thioalkylated products 4,5; 6,7; and 8,9 respectively. The isolation of these products provides the first example of the ability of pyranonaphthoquinone antibiotics such as kalafungin 1 to undergo reductive thioalkylation at the C-4 position. Reduction of a kalafungin analogue with sodium dithionite in the presence of thiols affords thioalkylated products thereby supporting the proposal that these compounds undergo reductive thioalkylation.