SHORT COMMUNICATIONSSulprostone (I) is a metabolically more stable analog of prostaglandin E 2 , which is widely used in biomedical research [1,2] and is known in gynecologic practice as an efficient agent (in combination with RU-486 or without it) for abortion [3][4][5]. The chemical synthesis of sulprostone and structurally related compounds, N-methylsulfonyl-16-phenoxyprostaglandincarboxamides, was described in [6]. Corey et al. [7] obtained sulprostone from optically active aldehyde; it was isolated as a colorless powder with mp 78.5-79.5°C (from ethyl acetate-diethyl ether); however, no α D value was given. According to patent [8], the melting point of sulprostone is 76°C, but its optical rotation is also missing. Commercial sulprostone produced by Cayman has mp 84-86°C (purity ≥98%); insofar as its α D value is absent, it is not clear whether this product is racemic or optically active. To elucidate this problem and compare biological properties of the products we have synthesized racemic sulprostone according to a modified procedure [9].Using standard methods, stereoisomerically pure bis-trimethylsilyl ether II [9] was converted (through dihydroxy lactone III) into bis-ethoxyethyl ether IV which was reduced with i-Bu 2 AlH to the corresponding hydroxy lactone, and the latter was subjected to Wittig olefination with ylide generated from triphenylphosphonium salt V. The final steps in the synthesis of I were oxidation of the hydroxy group in VI with Collins' reagent and removal of protecting groups by acid hydrolysis.Sulprostone (I) thus obtained was purified first by column chromatography on silica gel and was then II, R = Me 3 Si; III, R = H; IV, VI, R = CH 3 CH 2 OCH(CH 3 ); a: 3% HCl-THF, yield 95%; b: ethyl vinyl ether, CH 2 Cl 2 , PPTS, yield 93%; c: i-Bu 2 AlH, CH 2 Cl 2 , -78°C, yield 95%; d: [Ph 3 P + (CH 2 ) 4 CONHSO 2 CH 3 ]Br -(V), t-BuOK, THF, 0°C, 1 h, yield 80%; e: CrO 3 · 2 Py, yield 85%. e, a O HO OH
