Acetic Acid → 6-[(E)-3-tert-butyldimethylsilyloxy-3-cyclohexylprop-1-enyl]-3-(5-ethoxycarbonyl-2-hydroxypent-2-yl)bicyclo[3,3,0]octan-2-one

Participants

Reaction Conditions

Reaction Steps

(E)-2-(3-tert-Butyldimethylsilyloxy-3-cyclohexylprop-1-enyl)bicyclo[3,3,0]octan-6-one, (65 mg), prepared as described in Reference Example 37 and in the form of (±)-(E)-2β-(3β-tert-butyldimethylsilyloxy-3-cyclohexylprop-1-enyl)bicyclo[3,3,0]octan-6-one was dissolved in dry tetrahydrofuran (2.63 ml). The solution was cooled to to -70° C. under an atmosphere of argon and treated with a solution of lithium bis(trimethylsilyl)amide in tetrahydrofuran (0.212 ml; 1M), and the mixture was stirred at -70° C. for 10 minutes. The mixture was then treated with ethyl 5-oxohexanoate (55 mg) and stirred for a further period of 5 hours at -70° C. The solution was treated with a solution of glacial acetic acid (0.02 ml) in diethyl ether (0.175 ml) and the mixture was allowed to warm to the ambient temperature. The mixture was then treated with water (20 ml) and extracted with ethyl acetate. The extract was washed with saturated aqueous sodium bicarbonate solution and then with saturated aqueous sodium chloride solution, dried over anhydrous sodium sulphate, and concentrated under reduced pressure. The residual oil was subjected to medium pressure, short column chromatography on silica gel, using a mixture of ethyl acetate and hexane (1:6 v/v) as eluant, to give 6-[(E)-3-tert-butyldimethylsilyloxy-3-cyclohexylprop-1-enyl]-3-(5-ethoxycarbonyl-2-hydroxypent-2-yl)bicyclo[3,3,0]octan-2 -one (22 mg), in the form of 6β-[(E)-3β-tert-butyldimethylsilyloxy-3-cyclohexylprop-1-enyl]-3-(5-ethoxycarbonyl-2-hydroxypent-2-yl)bicyclo[3,3,0]octan-2-one, otherwise known as (±)-ethyl(13E)-(9S,15R)-6a-oxo-6,9-methano-15-tert-butyldimethylsilyloxy-15-cyclohexyl-5-hydroxy-5-methyl-16,17,18,19,20-pentanorprosta-13-dienoate.

Provenance & Evidence