7-β- and 10-β-Hydroxylated congeners of CAF-603; elucidation of absolute configuration of CAF-603 family, and their SAR studies in the anti-fungal activity

Novel 7-β- and 10-β-hydroxylated congeners of CAF-603 (4 and 5, respectively) were isolated from Trichoderma crassum. Relative configuration of 4 was determined by NOE experiments. Stereochemistry of 7-β-hydroxy group in 5 was established by a combination of vicinal 3JH–H analyses and quantum chemical calculations. Absolute configurations of 4 and 5 were established by observing the Cotton effects of their bis(2-naphthoate) esters. T. crassum also produce known CAF-603 (1), 14-hydroxy and 8,9-β-epoxy derivatives (2 and 3, respectively). Present study first established the absolute configuration of CAF-603 family by taking their biosyntheses into account. Preliminary biological experiments revealed that the molecular target strictly recognizes the β-side of the cycloheptane ring.