Synthetic Approach to Cytochalasins

Studies directed toward total synthesis of cytochalasin B (1) and A (2) are described. A simple acyclic unit, 12, intended for incorporation into the macrolactone ring of the cytochalasins has been prepared in seven steps from citronellol (5). The isoindolone nucleus 36 has been prepared by a Diels-Alder strategy via adduct 31. Conversion of this adduct to methoxy lactam 33 and coupling with tribenzylaluminum afforded lactam 34. Hydroxylation of the enolate of 34 gave isoindolone 35 containing the five chiral centers necessary for preparation of 1 and 2. Debenzylation of 35 produced diol 36, which will be combined with fragment 12 to ultimately complete a cytochalasin total synthesis.