摘要:
The invention relates to a process for the preparation of optically active .alpha.-hydroxycarboxylic acids characterised in that carbamates are first reacted in the presence of a selective base and of a chelate-forming diamine to give a carbanion complex compound, this is then dia- or enantioselectively deprotonated, then substituted with CO.sub.2 and, as a final step, the heterocyclic protective group is eliminated.
摘要:
A process for the preparation of a compound of the formula ##STR1## which comprises deprotonating a carbamate of the formula ##STR2## in an inert solvent with a selective base, in the presence of a chelate-forming diamine to give a compound of the formula ##STR3## and then reacting III in an inert solvent, either with an achiral electrophile of the formula (IV) or (V) or with an optionally prochiral electrophile of the formula (VI) ##STR4## and in the case in which R.sup.1 represents an electrofugic leaving group, optionally again electrophilically substituted with the formation of an acyl anion and renewed deprotonation, and in a last step, solvolytically removing the protecting group --CO--NR.sup.10 R.sup.11.
摘要:
Compounds which themselves are antibacterially active and/or which are useful as intermediates for producing antibacterially active materials such as penicillins and cephalosporins are obtained by the following syntheses:Benzyl-2-(2,2-dimethyl-1,3-dioxan-5-ylidene)-2(N-formyl-1)-aminoacetate to benzyl-2,2-dimethylspiro-[1,3-dioxane-5,5'-1',3-thiazoline]-4'-carboxylate to benzyl 2-(2,2-dimethyl-1,3-dioxan-5-ylidene)-2[N-(methylthiomethylene)-amino] acetate to benzyl 2-(trans-3-azido-4-methylthio-2-oxo-1-azetidinyl)-2-(2,2-dimethyl-1,3-dioxan-5-ylidene) acetate to benzyl 2(trans-3-benzoylamino-4-methylthio-1-azetidinyl)-2-(2,2-dimethyl-1,3-dioxan-5-ylidene) acetate to either (1) benzyl 2-(7-oxo-3-phenyl-4-oxa-2,6-diazabicyclo[3.2.0]hept-2-en-6-yl)-2-(2,2-dimethyl-1.3-dioxan-5-ylidene)acetate or (2) benzyl 2-(trans-3-benzoylamino-4-chloro-1-azetidinyl)-2-(2,2-dimethyl-1,3-dioxan-5-ylidene) acetate and then to the product benzyl-7-benzoylamino-1-dethia-1-oxa-3-hydroxymethyl-cephem-4-carboxylate.