Bitter principles of the Cucurbitaceae. Part XV. Cucurbitacins from a hybrid of Lagenaria siceraria

Abstract

The two main triterpenoids in the fruits of a Lagenaria siceraria hybrid have been isolated and their structures determined by physical measurements, notably nuclear magnetic resonance and circular dichroism, on suitable derivatives. The major component is formulated as 22-deoxocucurbitacin D and the minor compound as an α-ketol isomer, 22-deoxoisocucurbitacin D. In each of these compounds, mild treatment with acid resulted in elimination of the hydroxyl group at position-25 and concomitant formation of an ether bridge between positions-16 and -23.