Stereoselective synthesis of polyether antibiotics, lasalocid A and isolasalocid A, via a chelation-controlled formation of tetrahydrofuran rings under thermodynamic conditions

Article abstract of DOI:10.1016/S0040-4039(00)98022-5

The B-rings (2,5-trans-tetrahydrofurans) of lasalocid A (6) and isolasalocid A (7) were stereoselectively constructed from the corresponding p-methoxyphenylallyl alcohols (13a, 13b) by treatment with ZnBr₂ to give C₁₃-C₂₄ fragments (14a, 14b) via a new chelation-controlled cyclization under thermodynamic conditions. After their conversion into lasalocid ketone (19) and BOM-isolasalocid ketone (20), coupling with the C₁-C₁₁ aldehyde (22) completed the synthesis of 6 and 7, respectively.