Aldol-type transformations of levoglucosenone-derived medium-sized keto lactones

Action of bases on levoglucosenone-derived 6-oxononan-9-olide and 7-oxodecan-10-olide causes the transannular reaction of the aldol type affording stable 2-acylcyclopent-1-en-1-ol and 2-acylcyclohex-1-en-1-ol, respectively. The lower homologue, 5-oxooctan-8-olide derivative, under the similar conditions gives a complex mixture of products, which may be explained by the poor stability of the intermediate 2-acyl-cyclobut-1-en-1-ol.