Sulfur-containing Dioxopiperazine Derivatives from Emericella heterothallica

Emethacins A (1) and B ( 2 1 , sulfur-containing dioxopiperazines, were isolated from Emericella heterothallica ATCC 16824, along with three dioxopiperazine derivatives -(3-5).Emethacin B was identical with (3g,6R)-3,6-dibenryl-3,6-bis(methylthio)-2,5-dioxopiperazine (2) which had been already isolated from Asperqillus s.The structure of the new compound, emethacin A ( I ) , was confirmed by spectro-~c o p i c and chemical correlation as (31?,6~)-3-benzyl-6-benzylidene-3-methylthio-2.5-dioxopiperazine.Compound 3 was ( 3 5 , 65)-3-benzyl-6benzylidene-2.5-dioxopiperazine, which was the enantiomer of the compound 7 isolated from Streptomyces noursei.Recently the antifungal epidithiodioxopiperazines, emestrin2 and dithiosilva-tinr3 were isolated from Emericella striata (Rai, Tewari & Mukerji) Malloch & Cain and Asperqillus silvaticus Fennell & Raper, respectively.In the course of screening for dioxopiperazine derivatives from Emericella spp.. a novel 4 pyrazinone derivative designated emeheterone ( 6 ) was isolated from Emericella heterothallica (Kwon, Fennel1 & Raper) Malloch & Cain (mating type a), strain ATCC 16824.We are reporting in this paper the isolation of two sulfur-containing dioxopiperazines designated emethacins A (1) and B (2) from the same extract, along with two dioxopiperazines (3 and 4 ) .Another dioxopiperazine