合成路线1

The compound was originally isolated from the fungal source N. gypsea var. incurvata. The synthesis of this compound was further described. Treatment of N-phthaloyltryptophan methyl ester (I) with tert-butyl hypochlorite and triethylamine at -78 C led to the formation of the intermediate 3-chloroindolenine (II), which was reacted with B-prenyl-9-BBN (III) to yield the 3-(1,1-dimethylpropenyl)indole (IV). Removal of the phthalimide protecting group of (IV) by hydrazinolysis provided aminoester (V). Protection of (V) as the tert-butyl carbamate, followed by ester hydrolysis with LiOH afforded the N-Boc-amino acid (VI). Coupling of protected amino acid (VI) with aminoester (V) by means of BOP-Cl gave dipeptide (VII). After removal of the Boc protecting group of (VII) with trifluoroacetic acid, ammonia-catalyzed cyclization provided diketopiperazine (VIII). Alternatively, diketopiperazine (VIII) was obtained by thermal cyclization of two molecules of aminoester (V) at 140 C. Oxidative cyclization by means of dimethyldioxirane (IX) produced a 1:1:2 mixture of syn:syn, anti:anti, and syn:anti diastereoisomeric heptacyclic compounds. Finally, the target syn:anti isomer was isolated by chromatography.