Aldol condensation reactions of tricarbonyliron complexes. Towards building blocks for the synthesis of carbomycin B/tylosin macrolide antibiotics and fluorinated analogs

Tricarbonyliron complexes of alpha-methoxyheptadienone 3 and octadienone 8 were reacted as silyl enol ethers with protected beta-hydroxypropanal and T iCl4, to give the syn-syn aldol condensation products 4 and 11 as major, is olated diastereomers (61 and 45%), Products 4 and 11 were converted into ke y intermediates of previous total syntheses of carbonolide B and tylonide, in a few steps, including the iron-directed reduction to syn diols and part ial ozonolysis. The same methodology was used for the high yielding synthes is of a monofluorinated analog. (C) 2000 Elsevier Science Ltd. All rights r eserved.