Efficient Synthesis of cis- and trans-3,4-Dihydroxy-3,4-dihydromollugin

Abstract

An efficient synthesis of naturally occurring compounds isolated from Pentas longiflora, cis-3,4-dihydroxy-3,4-dihydromollugin 2, and trans-3,4-dihydroxy-3,4-dihydromollugin 3 is described. The O-protected mollugins were dihydroxylated using OsO4 to achieve the corresponding cis-dihydroxy derivatives in excellent yield. The synthesis of trans-3,4-dihydroxy-3,4-dihydromollugin was achieved using Oxone in good yield. A mechanism for the formation of cis-3,4-dihydroxymollugin acetonide from the reaction of mollugin with Oxone is proposed.

Busseihydroquinones A–D from the Roots of Pentas bussei

“…Hence, 2 was identified as the new 1-hydroxy-4-methoxy-3′,3′-dimethyl-3 H -benzo[ f ]chromene-2-carboxylic acid and was given the trivial name busseihydroquinone B. It should be noted that 2 is isomeric to mollugin, a natural product isolated from Pentas longiflora and synthetically extensively explored by De Kimpe et al − …”

Osmium-free direct syn-dihydroxylation of alkenes

“…Although oxone is known to lead to direct alkene oxidation to trans-diols, 67 de Kimpe et al reported the unusual formation of a protected cis-diol via oxone-mediated syn-dihydroxylation in 2008 (Scheme 54). 68 The reaction was investigated en-route to the synthesis of cis-3,4-dihydroxy-3,4-dihydromollugin. The reaction was not fully stereoselective but variation of the reaction conditions can favour cis over trans-diols.…”

Metal-free syn-dioxygenation of alkenes

“…10 De Kimpe and co-workers have described an unprecedented example of Oxone mediated syn-dioxygenation of mollugin 15 (Scheme 5). 11 Scheme 1 Cyclopropyl malonoyl peroxide 3 mediated dihydroxylation.…”