Preparation of dendrobine intermediate ethyl cyclopentenyl ester using RCM strategy.

Ethyl 2-methylcyclopent-2-ene-1-carboxylate (3) is an important building block in the synthesis of some natural products. In this paper, 2GGC was used for the RCM reaction to prepare this scaffold instead of reported 1GGC. This scaffold (3) was obtained in a moderate yield and its structure was determined by 1H NMR and 13C NMR. A contra-ring closing metathesis mechanism was also put forward to explain the formation of the product. [ABSTRACT FROM AUTHOR]