Organocatalytic Asymmetric Sulfa-Michael Addition of Thiols to 4,4,4-Trifluorocrotonates
摘要:
The first asymmetric sulfa-Michael addition of thiols to 4,4,4-trifluorocrotonates for the construction of a stereogenic center bearing a unique trifluoromethyl group and a sulfur atom has been achieved in high yields and excellent enantioselectivities with a 1 mol % bifunctional organocatalyst. Subsequent transformation led to the expedient preparation of enantioenriched thiochroman-4-one and the key intermediate of the potent inhibitor of MMP-3, (R)-gamma-trifluoromethyl gamma-sulfone hydroxamate.
The gamma-trifluoromethyl gamma-sulfone hydroxamate 1 was synthesized both in racemic and enantiomerically pure forms by means of a thia-Michael reaction of p-methoxythiophenol on achiral and chiral 3,3,3-trifluorocrotonoyl Michael acceptors. The (R)-1 enantiomer was the most potent inhibitor of MMP-3 (stromelysin-1), showing an IC50 = 3.2 nM, as well as the most selective with respect to MMP-9 (65-fold). (c) 2005 Elsevier Ltd. All rights reserved.