References

Our paper: Peng, F.; Danishefsky, S. J. Am. Chem. Soc. 2012, 134, 18860-18867.

For the description of Epoxidation using DMDO, the paper referenced: Stachel, S. J.; Danishefsky, S. J. Tetrahedron Letters 2001, 42, 6785-6787.

This paper focused on the synthesis of epothilone B, a compound part of a group of molecules known as epothilones (Figure 1). Epothilones are of interest in that they have been shown to be potential anticancer agents. The final step in the synthesis of epothilone B involves the epoxidation of 12, 13-desoxyepothilone B. Using 2,2’-dimethyldioxirane (DMDO), epoxidation occurs with excellent stereoselectivity as well as high confidence and yield. In contrast, when mCPBa was used three regions were susceptible to oxidation creating a different major product. The diastereoselectivity using DMDO, which favored the β-stereoisomer over the α-stereoisomer, was shown to be highly temperature dependent. As the reaction temperature is increased, the diastereoselectivity decreases. The highest yield was observed at -78oC, with a diastereoselectivity ratio of greater than 25:1. Overall, this paper demonstrated Epothilone B can be produced with great stereoselectivity using DMDO if the correct experimental protocols are followed.

Other Articles that also cite the referenced one above:

Citation 1: Jung, J.-C.; Rajashaker, K.; Vines, K. K.; Zheng, Y.-S.; Bijoy, P.; Valluri, M.; Avery, M. A. J. Org. Chem. 2004, 69, 9270-9284.

Reasoning: This paper saw a dramatic change in diastereoselectivity when 3,3-dimethyldioxirane was used for epoxidation. The β epoxide was favored over the α epoxide, supporting Stachel and Danishefsky’s findings.

Citation 2: Yoshimura, F.; Rivkin, A.; Gabarda, A. E.; Chou, T.-C.; Dong, H.; Sukenick, G.; Morel, F. F.; Taylor, R. E.; Danishefsky, S. J. Angew. Chem. Int. Ed. 2003, 42, 2518-2521.

Reasoning: A main step of this reaction also utilized 2,2’-dimethyldioxirane (DMDO) for epoxidation. This paper found that α epoxidation was favored when DMDO was used with (E)-9, 10-dehydro-dEpoB unlike how β epoxidation to be favored with others.