Studies on the syntheses of benzoquinone ansamycin antibiotics. Syntheses of the C5-C15 subunits of macbecin I, geldanamycin, and herbimycin A.

[reaction: see text] A general and convergent route to the C(5)-C(15) subunits of the benzoquinone ansamycin antibiotics macbecin I, geldanamycin, and herbimycin A is described. Each subunit is prepared by the stepwise coupling of differentially functionalized aldehydes with a pentenyl dianion equivalent derived from diastereoselective pentynylation and regioselective reductive coupling.