The unexpected forma on of compound 8 during the lithia on/I2-mediated oxida on sequence with methyl ester 2 endo,endo can be a ributed to stereochemical factors. Deprotona on of compound 2 endo,endo (Step A, Scheme 2) leads to the enolate I1, which readily undergoes intramolecular nucleophilic a ack on the ester group (B) due to the favorable geometry of the intermediate. The subsequent elimina on (C) results in the forma on of ketone 8. Furthermore, the observed results demonstrate the reversibility of Steps B and C as 8 yields a diastereomeric mixture of diester 2 under higher temperatures in the presence of NaOMe. Scheme 2. The presumable mechanism of 2 endo,endo diester epimeriza on.