Org Prep Daily

September 26, 2006


Filed under: procedures — milkshake @ 9:38 pm

A sulfuric acid solution obtained by combining 95.5% sulfuric acid 12.60g (122.7mmol) with ice 12g was gradualy added to a mixture of L-Prolinol 12.50g (123.5mmol) and ice 12g with cooling on ice bath (exothermic). The obtained solution was concentrated on rotavap (R.T. to 80C at 8 Torr). The obtained oily residue was heated and rotated on Kugelrohr air bath at 5-8 Torr at 110C for 10 min, the air bath temperature was then increased 130C and, after additional 15 min, to 150C. The heating at 150C was continued for 30 min. The obtained solid material was cooled to R.T.,  dissolved in a mix of water 20mL and ethanol 10mL at reflux, additional ethanol 20mL was added and the mixture was allowed to crystallize at R.T. for 5 hours. The crystallized product was collected by filtration, washed with ethanol 30mL and dried on highvac. (17.129g of crystalline solid) A second crop was obtained by diluting the supernatants with ether 60mL, shaking vigorously for 5 min, collecting the precipitate by filtration and washing with ethanol (Second crop: 2.214g of crystalline solid). Combined Y= 19.343g (86.5%) of L-prolinol-O-sulfate as a white crystalline solid.

1H(d6-DMSO, 400MHz): 8.990(br s, 1H), 8.464(br s, 1H), 3.997(dd, 12.1Hz, 3.9Hz, 1H), 3.843(dd, 11.7Hz, 8.2Hz, 1H), 3.701(m, 1H), 3.114(m, 2H), 1.981(m, 1H), 1.831(m, 2H), 1.578(m, 1H); 13C(d6-DMSO, 100MHz): 65.54, 59.57, 46.02, 26.78, 24.00

L-prolinol-O-sulfate 18.970g (104.7mmol) solution in water 150mL was gradualy added into a vigorously-distilling 20% NaOH (310mL) in a distillation apparatus with ice-cooled receiver over 15 minutes. The distillation was continued until distilates were no longer fishy-smelling. The distillates were cooled on ice, saturated with solid KOH , extracted with ether 250mL and re-extracted twice with additional ether (2x100mL). The combined extracts were dried with Na2CO3 and carefully concentrated, the residue was distilled at atmospheric pressure through a short (2in) Vigreaux column. A pure product fraction distilled at 105-110C. Y=4.179g (48%) of a colorless liquid with an intense irritant fishy odor.

1H(D2O, 400MHz): 2.687(dd, 11.7Hz, 8.6Hz, 1H), 2.550(m, 1H), 2.146(m, 1H), 1.827(dd, 12.9Hz, 8.2Hz, 1H), 1.620(m, 1H), 1.397(m, 1H), 1.309(d, 5.4Hz, 1H), 1.246(m, 1H), 1.139(d, 3.9Hz, 1H); 13C(D2O, 100MHz): 51.00, 39.42, 25.96, 25.14, 19.08

JOC 32, 2388-91 (Gassman et al)

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