合成路线1

The title compound was isolated from the fermentation broth of Streptomyces sp. strain HC-21. A synthetic method for the preparation of the title compound was also reported. Asymmetric dihydroxylation of ethyl crotonate (I) using commercial AD-mix-beta produced diol (II). This was converted to the (2S,3R)-epoxide (III) by bromination with HBr in HOAc followed by cyclization of the resultant bromohydrin in the presence of DBU. Epoxide ring opening with the organomagnesium reagent generated from indole (IV) and methylmagnesium bromide furnished the chiral indolylbutanoate (V). Cyclization of the hydroxy ester (V) with guanidine hydrochloride (VI) in the presence of potassium tert-butoxide yielded the amino oxazolone (VII). Finally, displacement of the amino- by a methylamino group was achieved by treatment with aqueous methylamine.