Enantioselective Michael additions on α,β-unsaturated N-acylated oxazolidin-2-ones using mild scandium triflate catalysis
作者:Sami J.K. Sauerland、Eero Kiljunen、Ari M.P. Koskinen
DOI:10.1016/j.tetlet.2005.12.076
日期:2006.2
The asymmetric conjugateaddition of thiophenol to (E)-3-crotonoyloxazolidin-2-one catalysed by the scandium(III) triflate complex of Ph-PYBOX gave the corresponding adduct in 66% ee. Lanthanoid triflates gave lower enantioselectivities (⩽28% ee).
(S)-Alkyl 3-(thien-2-ylthio)butyrate and analogs and synthesis thereof
申请人:Merck & Co., Inc.
公开号:US04968814A1
公开(公告)日:1990-11-06
(S)-Alkyl 3-(thien-2-ylthio)butyrate and analogs are intermediates in the synthesis of the chiral (S,S)-5,6-dihydro-4-ethylamino-6-methyl-4H-thieno[2,3-b]thiopyran-2-sulfon amide-7,7-dioxide and analogs thereof, topically effective carbonic anhydrase inhibitors useful in the treatment of ocular hypertension and glaucoma.
An enantioselective synthesis of the topically-active carbonic anhydrase inhibitor MK-0507: 5,6-dihydro-(S)-4-(ethylamino)-(S)-6-methyl-4H-thieno[2,3-b]thiopyran-2-sulfonamide 7,7-dioxide hydrochloride
作者:Thomas J. Blacklock、Paul Sohar、John W. Butcher、T. Lamanec、E. J. J. Grabowski
DOI:10.1021/jo00059a013
日期:1993.3
The key feature in the synthesis of topically-active carbonic anhydrase inhibitor MK-0507 (13b) is a Ritter reaction that exhibits an unexpected tendency to proceed with retention of chirality. This phenomenon was further studied on model compounds free from potential diastereomeric effects. A mechanism involving transannular stabilization of the sp2-hybridized center by sulfone oxygen is proposed with the net result of double inversion. A second key feature in the preferred sequence to MK-0507 involves the classic problem of how to maximize substitution over elimination. This problem manifests itself in the stereospecific alkylation of 2-mercaptothiophene with derivatized methyl (R)-3-hydroxybutyrate and is compounded by a subsequent Michael reaction leading to a loss of product chirality. Results are presented that eliminate this problem.
Stereochemical studies on the reactions catalyzed by the PLP-dependent enzyme 1-aminocyclopropane-1-carboxylate deaminase
作者:Hungwen Liu、Richard Auchus、Christopher T. Walsh