Efficient and selective synthesis of siphonarienolone and related reduced polypropionates via Zr-catalyzed asymmetric carboalumination

Siphonarienolone (1) has been synthesized from siphonarienal (3) in 66% over four steps. Synthesis of 3, in turn, has been achieved in two steps (85% combined yield) from 4, prepared from 3-buten-1-ol in seven steps (23% combined yield). Also, a two-step conversion of 3 into siphonarienone (2) is reported.