Diazald → Methyl cholate

Beteiligte Stoffe

Reaktionsschritte

Cholic acid (1a) (2.0 g, 4.9 mmol) in THF (40 ml) at 0° C. was treated dropwise with freshly prepared diazomethane in ether (prepared in the usual manner from diazald: diazald is N-methyl-N-nitroso-p-toluenesulphonamide) until the yellow colour persisted. After 15 minutes at 0° C. the solvent was evaporated to yield a white foam (2.1 g, 100%). Recrystallisation from methanol afforded pure methyl cholate1 (1.3 g, 63%): m.p. 158°-159° C. (crystals began to melt 86°-88° C. and then resolidified--this was probably due to the retention of methanol in the crystals, see NMR data) [Lit1 156°-158° C.]; 1H NMR (60 MHz; CDCl3) δ0.66 (3H, s, 18-CH3), 0.87 (3H, s, 19-CH3), 3.0-3.6 (1H, m. 3β-H), 3.2-3.5 (3H, m [exchanges on adding D2O], 3α, 7α and 12α OH's), 3.48 (s, MeOH of crystallisation [ca. 1 mol equiv.]), 3.65 (3H, s, 24-OMe), 3.7-3.9 (1H, m, 7β-H), 3.8-4.0 (1H, m, 12β-H); IR (nujol mull) 3392, 3300 (OH's), 1734 (C=O) cm-1.

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