Studies of Fungal Products. XII. Structure of Aurantioemestrin from Emericella striata

Abstract

The structure of aurantioemestrin (I), d new degradated dioxopiperazine isolated from Emericella striata (80-NE-221, was established as 1 on the basis of spectroscopic evidences.Aurantioemestrin (1). a dloxopiperazinethione, seems to be the biogenetical key intermediate from emestrin ( 3 ) to dethiosecoemestrin ( 2 ) .Previously we reported2 the structural determination of dethlosecoemestrln 12).and the isolation of aurantioemestrin (1).both obtained from the methylene chloride extract of Emericella striata (Rai, Tewari E Mukerii) Malloch 8 Caln, strain 80-NE-22.The structural elucidation of l3 is to be reported in this paper.Aurantioemestrin ( 1 ) , mp 118-120°C (dec.I, ~o ] ~~~ -556-, was isolated from the fraction slightly less polar than dethiosecoemestrin (21, of the methylene chloride extract of the culture filtrate.A sllghtly positive sllver nitrate test (pale brown) suggested the presence of sulfur atom in 1.The molecular formula of 1 was confirmed as C H N 0 S from high resolution ms and elemental 27 20 2 9analysis.The 'H and 13c nmr spectra of 1 were closely similar to those of 2, except the downfield shift of the protons assigned to N-methyl group at 63.292 in 2 to at 6 3.665 i n 1, and the carbon signal at 6 187.05 (Sq) In 1 instead of that at 6 157.45 (Sq).(Tables 1 and2) The compound 1 was found to be easlly degradated to dethlosecoemestrin ( 2 ) .So aurantioemestrin ( 1 )* The assignments may be reversed COOH CHOOMe OH