~~~~~~ ~The 4-epiverrucarin A (24), a new unnatural macrocyclic trichothecene, was synthesized starting from 4-epiverrucarol(20). The latter was obtained by metal-hydride reduction of the 4-0x0 derivative 19. Subsequent conversion of 20 into the monoester 30 and then the diester 32 followed by macrolactonization of the latter yielded 4-epiverrucarin A (24). Attempts to invert the configuration of the naturally occuring 3a-OH group of a tricholhecene were unsuccessful. The cytostatic (P-8 15) and immunosuppressive (MLR) activity of several natural and unnatural trichothecenes was determined in v i m .Introduction. -In the preceeding communication [ 11, first results of our programme directed to the synthesis of new unnatural macrocyclic trichothecenes were described, namely the synthesis of 3-isoverrucarin (( 1"-0 )(4+3)abeo-verrucarin A; 1) and the two novel macrocyclic by-products verrucinol and verrucene (2). In continuation of these efforts, the next goal was the preparation of 3-and 4-hydroxytrichothecenes possessing unnatural configurations and to use them for the synthesis of additional macrocyclic analogues of verrucarin A (3). Such compounds will give more detailed information on the relationship between chemical structure and biological activity.