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With hydrogenchloride; triethylamine; In N-methyl-acetamide;
A. Preparation of N-protected lactam formic acid of Formula 2. To a 0 solution of the unprotected lactam, <strong>[87791-58-0]azetidinone-4-carboxylic acid benzyl ester</strong> (4.1 g, 20 mmol) prepared as described in U.S. Pat. No. 4,290,947, in 15 mL of sieve dried dimethylformamide (DMF) was added t-butyldimethylsilyl chloride (3.165 g, 21 mmol) followed by triethyl amine (2.93 mL, 21 mmol). After stirring at 0 for 40 minutes the reaction mixture was diluted with petroleum ether (200 mL) (low boiling) and washed with water. The organic layer was washed successively with 75 mL portions of water, 2N HCl, H2 O, brine and then dried over MgSO4. Removal of the solvent gave N-t-butyldimethylsilyl <strong>[87791-58-0]azetidinone-4-carboxylic acid benzyl ester</strong> as a mobile oil in 93% yield (5.856 g).
EXAMPLE 1 1-p-nitrophenylsulfonyl-4-benzyloxycarbonyl azetidin2-one Diazabicycloundecane (152 mg, 1 mM) was added to a mixture of 205 mg (1 mM) <strong>[87791-58-0]4-benzyloxycarbonyl azetidin-2-one</strong> and 181 mg (1 mM) p-nitrobenzenesulfonyl chloride in 10 ml methylene chloride at room temperature. After stirring 21/2 hours, the orange solution was washed with water, dried over MgSO4, and concentrated in vacuo. The residue was chromatographed on silica gel in hexane/ethyl acetate to yield 64 mg (17%) of 1-p-nitrophenylsulfonyl-<strong>[87791-58-0]4-benzyloxycarbonyl azetidin-2-one</strong>. NMR (CDCl3): delta 3.3 (2H, doublet-quartet), 4.8 (qt. 1H), 5.2 (s, 2H), 7.2 (s, 5H), 8.2 (mlt. 4H).
(S)-benzyl 1-hydroxymethyl-4-oxo-2-azetidinecarboxylate[ No CAS ]
[ 103700-21-6 ]
Yield
Reaction Conditions
Operation in experiment
With formic acid;
REFERENCE EXAMPLE 3 (Raw Material of Example 4) STR42 To a mixture of 10 ml of formic acid and 20 ml of formalin was added 3 g of <strong>[87791-58-0](S)-benzyl 4-oxo-2-azetidine-carboxylate</strong> (14). The resulting mixture was kept at 50 C. for 15 minutes. After cooling, the mixture was made alkaline with a saturated sodium bicarbonate aqueous solution and extracted twice with 50 ml of ether. The ethereal extracts were washed with a saturated sodium chloride aqueous solution and then dried. The solvent was removed by distillation under reduced pressure and the residue thus obtained was purified by column chromatography using silica gel. Thus, 970 mg of (S)-benzyl 1-hydroxymethyl-4-oxo-2-azetidinecarboxylate (15) and 1.78 g of (S)-benzyl 1-formyloxymethyl-4-oxo-2-azetidinecarboxylate (16) were obtained.
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