220571-38-0Relevant academic research and scientific papers
Unexpected effect of protecting group and solvent on the stereoselectivity of m-CPBA epoxidation of diprotected cis-4,5- dihydroxycyclohexenes
De Sousa,Kee,O'Brien,Watson
, p. 387 - 390 (1999)
The stereoselectivity of m-CPBA epoxidation of diprotected cis-4,5- dihydroxycyclohexenes has been studied as a function of protecting group, solvent and in one example, epoxidising reagent. Three different ways of obtaining high levels of trans diastereoselectivity have been uncovered. In addition, the results suggest that bulky silyl protecting groups (eg triethylsilyl and tert-butyldimethylsilyl) can, in CH2Cl2, behave as moderate cis-directors via hydrogen bonding to m-CPBA.
Optimisation of enantioselectivity for the chiral base-mediated rearrangement of bis-protected meso-4,5-dihydroxycyclohexene oxides: Asymmetric synthesis of 4-deoxyconduritols and conduritol F
De Sousa, Simon E,O'Brien, Peter,Pilgram, Christopher D
, p. 4643 - 4654 (2007/10/03)
A strategy based on diastereoselective epoxidation of a cyclohexene followed by chiral lithium amide-mediated epoxide rearrangement has been used to synthesise an allylic alcohol building block of >95% ee. The key step is the enantioselective rearrangement of a bis-protected meso-4,5-dihydroxycyclohexene oxide. A range of protecting groups and chiral base structures were surveyed in order to find the optimum protocol for high enantioselectivity. Using a tert-butyldimethylsilyloxy protecting group and a norephedrine-derived chiral base, a 93% yield of an allylic alcohol of >95% ee was achieved. To demonstrate the synthetic utility, this allylic alcohol was subsequently transformed into 4-deoxyconduritols and (+)-conduritol F.
