反应详情

(2RS,3SR)-3-Methyl-2-tetrahydrofuroic acid 91.3 g) was converted to the acid chloride with oxalyl chloride (2.54 g, 1.75 mls) in dichloromethane (20 mls) as described in Example 1 (a). Diazomethane was passed through a solution of the acid chloride in dichloromethane (20 mls), cooled in ice/water until i.r. analysis showed no starting material. Hydrobromic acid (2 mls, 49% w/v aqueous solution), was added dropwise and the reaction mixture stirred vigorously for 10 min. T.l.c. analysis showed complete conversion to the title compound. The solution was washed with water, brine and dried. The solvent was washed with water, brine and dried. The solvent was evaporated and the residue flash chromatographed on silica gel, eluting with 5 and then 10% ethyl acetate/hexane to give the product as an almost colourless oil, (1.621 g, 79%); νmax (CH2Cl2) 1732 cm-1 ; δH (CDCl3) 0.96 (3 H, d, J 7.2 Hz), 1.70 (1 H, m), 2.17 (1 H, m), 2.70 (1 H, m), 3.93 (1 H, m), 4.12 and 4.25 (2 H, ABq, J 14.7 Hz) and 4.49 (1 H, d, J 7.3 Hz). [Mass spectrum: +ve ion (ammonia) MNH4 (224)].