中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | (3S,4S)-3-<(1R)-1-<(tert-Butyldimethylsilyl)oxy>ethyl>-4-<(1S)-1-(methoxycarbonyl)ethyl>azetidin-2-one | 87037-96-5 | C15H29NO4Si | 315.485 |
—— | (3S,4R)-3-<(1R)-1-<(tert-Butyldimethylsilyl)oxy>ethyl>-4-<(methoxycarbonyl)methyl>azetidin-2-one | 185446-92-8 | C14H27NO4Si | 301.458 |
—— | (3S,4S)-4-<(1S)-1-benzyloxycarbonylethyl>-3-<(1R)-1-tert-butyldimethylsilyloxyethyl>-2-azetidinone | 96035-98-2 | C21H33NO4Si | 391.583 |
—— | (3S,4R)-3-<(R)-1-tert-Butyldimethylsilyloxyethyl>-4-<(R)-1-methylallyl>-2-azetidinone | 96543-02-1 | C15H29NO2Si | 283.486 |
—— | (3S,4S)-3-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[1,1-di(allyloxycarbonyl)ethyl]-2-azetidinone | 150193-38-7 | C21H35NO6Si | 425.598 |
—— | 5-{3-[1-(tert-butyldimethylsilyloxy)ethyl]-4-oxoazetidin-2-yl}-2,2,5-trimethyl-[1,3]dioxane-4,6-dione | 156630-83-0 | C18H31NO6Si | 385.533 |
—— | (2R)-2-[(2S,3S)-1-[tert-butyl(dimethyl)silyl]-3-[(1R)-1-[tert-butyl(dimethyl)silyl]oxyethyl]-4-oxoazetidin-2-yl]propanoic acid | 188193-06-8 | C20H41NO4Si2 | 415.721 |
—— | (3S,4R)-3-[(R)-1-(tert-butyldimethylsilyloxy)ethyl-4-vinyl-2-azetidinone] | 112256-72-1 | C13H25NO2Si | 255.432 |
—— | (3S,4R)-3-<(1R)-1-<(tert-Butyldimethylsilyl)oxy>ethyl>-4-<(1S)-1-<(2-thioxo-1,3-thiazolidin-3-yl)carbonyl>ethyl>azetidin-2-one | 112346-02-8 | C17H30N2O3S2Si | 402.654 |
—— | (3S,4R)-3-<(R)-1-(t-Butyldimethylsilyloxy)ethyl>-4-<(S)-1-((S)-4-isopropyl-2-oxazolidone-3-carbonyl)ethyl>-2-azetidinone | 102977-61-7 | C20H36N2O5Si | 412.602 |
—— | 5-((2S,3S)-1-(tert-butyldimethylsilyl)-3-((R)-1-(tert-butyldimethylsilyloxy)ethyl)-4-oxoazetidin-2-yl)-2,2,5-trimethyl-1,3-dioxane-4,6-dione | 156630-84-1 | C24H45NO6Si2 | 499.795 |
—— | (3S,4R)-3-<(R)-1-(t-Butyldimethylsilyloxy)ethyl>-4-<(S)-1-((S)-4-benzyl-2-oxazolidone-3-carbonyl)ethyl>-2-azetidinone | 109616-59-3 | C24H36N2O5Si | 460.646 |
中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | (3S,4S)-3-<(1R)-1-<(tert-Butyldimethylsilyl)oxy>ethyl>-4-<(1S)-1-(methoxycarbonyl)ethyl>azetidin-2-one | 87037-96-5 | C15H29NO4Si | 315.485 |
—— | (3S,4S)-4-<(1S)-1-benzyloxycarbonylethyl>-3-<(1R)-1-tert-butyldimethylsilyloxyethyl>-2-azetidinone | 96035-98-2 | C21H33NO4Si | 391.583 |
—— | (3S,4S)-1-(tert-butoxycarbonylmethyl)-3-<(1R)-1-tert-butyldimethylsilyloxyethyl>-4-<(1S)-1-carboxyethyl>-2-azetidinone | 105370-88-5 | C20H37NO6Si | 415.602 |
—— | (3S,4S)-4-<(1S)-1-benzyloxycarbonylethyl>1-(tert-butoxycarbonylmethyl)-3-<(1R)-1-tert-butyldimethylsilyloxy>-2-azetidinone | 105370-87-4 | C27H43NO6Si | 505.727 |
—— | (3S,4R)-3-<(1R)-1-<(tert-Butyldimethylsilyl)oxy>ethyl>-4-<(1S)-1-<(2-thioxo-1,3-thiazolidin-3-yl)carbonyl>ethyl>azetidin-2-one | 112346-02-8 | C17H30N2O3S2Si | 402.654 |
—— | (3S,4S)-1-(tert-butoxycarbonylmethyl)-3-<(1R)-1-tert-butyldimethylsilyloxyethyl>-4-<(1S)-1-phenylthiocarbonylethyl>-2-azetidinone | 105370-89-6 | C26H41NO5SSi | 507.767 |
The 4-chloroazetidinone 10, a very reactive chiral intermediate for 1-β-methylcarbapenems (1b), was easily prepared and isolated as a solid crystalline compound from the corresponding sulfide 5. Another chiral intermediate (16d) bearing the 1-β-methyl moiety was prepared by stereoselective aldol type condensation of either azetidinone 4 or 10 with metal enolates 14 (R = S—Bu′, M = ZrCp2Cl, [Formula: see text], and SnBr). The β/α ratios were 9:1, 3:1, 2:1 respectively.
In this study, a highly stereoselective preparation of (3S,4S)-3-[(1R)-1-tert-butyldimethylsilyloxyethyl]-4-[(1R)-1-carboxy-ethyl]-azetidin-2-one (2) is reported. It involves a Lewis acid mediated condensation of (3S,4R)-4-acetoxy-3-[(1R)-1-tert-butyldimethylsilyloxyethyl]azetidin-2-one (3) with simple O-silylenol ethers of thiopropionates. From all the examples reported in this paper the 2-picolyl thiopropionate or similar arrangements were found to be essential for this stereoselection. Finally, a mechanism involving chelation control seems to be operative.