- A practical method for the acylation of 2-imidazolidinone and 2-oxazolidinone chiral auxiliaries with 2-bromoacyl halides
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Optimised conditions for the acylation of (S)-4-(1-methyl-ethyl)-oxazolidin-2-one 4, (R)-4-phenyloxazolidin-2-one 5 and 4-(R), (5S)-1,5-dimethyl-4-phenylimidazolidin-2-one 3 with 2-bromoacyl halides were developed. For imidazolidin-2-one 3 the optimum con
- Candeias,Jenkins,Ribeiro,Afonso,Caddick
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p. 3241 - 3254
(2007/10/03)
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- Stereoselective dimerization of chiral α-bromoamides promoted by Fe(Co)5
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Organic α-bromocarboxylates react with aldehydes and ketones in the presence of Fe(CO)5 (the Reformatsky-type reactions). Unlike them, N-oxazolidinone derivatives of the same acids undergo diastereoselective reductive dimerization to give (2S,3S)-dimers, regardless of the configuration of the α-chiral center in the starting reagent.
- Kuznetsov,Khrustalev,Terentiev,Belokon'
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p. 548 - 550
(2007/10/03)
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- Heterocyclic compounds and their production
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A compound of the formula: STR1 wherein R1, R2, R3 and R4 are each a hydrogen atom, a lower alkyl group, an ar(lower)alkyl group or an aryl group, or R1 and R2 may be combined together to f
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- Highly stereocontrolled synthesis of the 1β-methylcarbapenem key intermediate by the Reformatsky reaction of 3-(2-bromopropionyl)-2-oxazolidone derivatives with a 4-acetoxy-2-azetidinone
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The key synthetic intermediate (4) of 1β-methylcarbapenems (1~3) was efficiently synthesized by employing highly stereocontrolled Reformatsky reaction (C4-alkylation) of 3-(2-bromopropionyl)-2-oxazolidone derivatives (6) with (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidino ne (5) in the presence of zinc dust followed by removal of 2-oxazolidone moieties. The best diastereoselectivity (β:α = 95:5) could be realized by uses of sterically crowded achiral 2-oxazolidone derivatives such as 4,4-dimethyl-, 4,4,5,5-tetramethyl, and 4,4-dibutyl-5,5-pentamethylene-2-oxazolidone and higher reaction temperatures (refluxing tetrahydrofran). The remarkable diastereoselectivities observed for the Reformatsky reactions could be explained by means of the weakly chelating transition state models.
- Ito,Sasaki,Tamoto,Sunagawa,Terashima
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p. 2801 - 2820
(2007/10/02)
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