Synthesis of Spiroketal-Modified Avermectin Analogs: 23-Nor-23-Oxa- and 23-Nor-23-Thia-Avermectins

Article abstract of DOI:10.1016/S0040-4039(00)73495-2

The concise synthesis of avermectin analogs wherein the C23 carbon has been excised and replaced with an oxygen or sulfur atom is described.The new, heteroatom-substituted avermectins represent isosteres of 22,23-dihydro-avermectin B_1a and, in the case of the sulfoxides and sulfones, are isosteric to avermectin B_2a.These new avermectins bear diverse functionality at C24 and C25.