Tetrabutylammonium Fluoride → (4R,5R,6R)-5-Acetylamino-4-hydroxy-6-(phenethylpropylcarbamoyl)-5,6-dihydro-4H-pyran-2-carboxylic acid

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Reaction Steps

To a stirred solution of (4R,5S,6R)-5-acetylamino-4-(tert-butyldiphenylsilanyloxy)-6-(phenethylpropylcarbamoyl)-5,6-dihydro-4H-pyran-2-carboxylic acid, methyl ester (7 g) in tetrahydrofuran (70 ml) was added tetra-n-butylammonium fluoride (12 ml of a 1M solution in tetrahydrofuran). After 4 hours at 23° C. the solvent was removed in vacuo and the residue was partitioned between brine and ethyl acetate. The organic extracts were dried over anhydrous sodium sulphate and the solvent was removed in vacuo to give an oil. This was chromatographed over silica (Merck 9385, 700 ml) using medium pressure (ca 4 psi) and dichloromethane/methanol (95:5 v/v) as eluant. The required fractions were combined and the solvent removed in vacuo to give the title compound as a pale yellow foam (3.98 g). 1H NMR (250MHz, CDCl3, rotamers) 7.3 (5H,m), 6.2 (1H, 2×d, J=4Hz), 5.1+4.9 (1H,2×d, J=6Hz), 4.6+4.5 (1H, 2×m), 4.4--4.2 (1H,2× m), 3.8 (3H, 2×s), 3.7--3.3 (4H, m), 3.0+2.8 (2H, 2×m), 2.0 (3H, 2×s), 1.8--1.3 (2H, m), 0.9 (3H, m); Mass spec. (low resolution) MH+ =405.

Provenance & Evidence