Formal convergent synthesis of ivermectin aglycone - A synthetic approach to the C10-C25 subunit of avermectins 2b
Abstract
A convergent, two-fragment synthesis of the C10-C25 northern moiety of avermectins has been developed. Along with our previous work in this area, the present contribution represents a formal synthesis of Ivermectin aglycone. Furthermore, according to a strategy leading to non y-pyranone adducts from, the condensation reaction between acetylacetone dianion and convenient aldehydes, 23-hydroxylated C10-C25 northern building blocks required for the synthesis of the avermectins series 2b were prepared. Subsequent unexpected kinetically favored unnatural (215)-spiro isomers were obtained under mild cyclization conditions.