Cyclic hydroxycarboxylic acids. I. Synthesis, stereochemistry and reactivity of 2,3-trans-2,3-Dihydroxycyclopentanecarboxylic acids

Abstract

Cyclopent-2-enecarboxylic acid and performic acid give a mixture of approximately equal amounts of the corresponding c-2,t-3- and t-2,c-3-dihydroxycyclopentane-r-1-carboxylic acids. The mixture was separated by chromatography of the methyl esters. Relative configurations were assigned from the action of tosyl chloride-pyridine on the separate acids. The c-2,t-3-dihydroxy acid yields a t-3-tosyloxy ,β-lactone and the t-2,c-3-dihydroxy acid yields a r-2-tosyloxy γ-lactone. Structures of the lactones were proved by correlating the products of acidic methanolysis and of alkaline hydrolysis with various derivatives of the acids. Proton magnetic resonance spectra are reported for 21 compounds from the two stereochemical families, including acetate, trifluoroacetate, tosylate and mesylate derivatives. Infrared data for relded lactones are tabulated. Formation of β-lactones from β-hydroxy acids by tosyl chloride appears to be unprecedented.