A simple and efficient route towards usefully functionalised six and seven-membered ring systems via α-hydroxycyclobutane rearrangement followed by retroaldol cleavage

Acid-catalysed rearrangement of α-hydroxycyclobutane derivative 10 followed by retroaldol cleavage and oxidation in an one-pot operation furnishes 18-methyl-1α, 4α-cycloheptane dicarboxylic acid 12 in excellent yield. With proper selection of starting α-hydroxycyclobutane derivative this methodology leads to highly functionalised [5-7] and [5-6] fused ring systems 17 and 20 respectively.