Pattern of incorporation of leucine samples asymmetrically labelled with 13C in the isopropyl unit into the C5-isoprenoid units of echinuline and flavoglaucine

Abstract

The labelling pattern of the C₅-isoprenoid moieties of echinuline (18) and flavoglaucine (19) obtained in feeding experiments of Aspergillus amstelodami of 90% enriched (4R)[5-¹³C]leucine (11) and of the (4S)-isomer (12), determined by ¹³C-n.m.r. spectroscopy, appears in agreement with a preferential incorporation of the carbon atom of the pro-S methyl group of the stereospecifically labelled amino acid (12) into the C-3 methyl group of the intermediate mevalonic acid and of the carbon atom of the pro-R methyl group of (11) in position 4, respectively.