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Prostaglandins II - an improved synthesis and structural proof of (±)-11-deoxyprostaglandin F1β

✍ Scribed by J.F. Bagli; T. Bogri

Publisher
Elsevier Science
Year
1967
Tongue
French
Weight
247 KB
Volume
8
Category
Article
ISSN
0040-4039

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✦ Synopsis

In an earlier communication ' from our laboratory we reported the total synthesis of a physiologically active analogue (V) of prostaglandin. The ssymmetric centres C-8, C-9 and C-l.2 were assumed to have configurations shown in the formula. In this communication, we report an improved synthesis and physicochemical evidences for the stereochemical assignments of (z)-lldeoxyprostaglandin Flj3. Tbe acid chloride (I)'on treatment with heptyne in the presence of aluminum chloride yielded the cblorovinyl ketone II (c21H3304c";u max.3 1735, 1685, 1590 cm-l; x max 248uq~ ( 4.00) 2; n.m.r. 0.86d 3H poorly resolved triplet, terminal methy14; 3.544 3H, methoxyl; 6.3OAl.H, vinyl proton singlet). Treatment of ketone II with sodium hydroxide in methanol yielded the enol-ether III (Cd3605;L'max 1735, 1670, 1574 Cm -l; h max 262mp (4.21); n.m.r. 0.85d3H terminal methyl, 3.53dand 3.626

3H each, methoxyls, 5.356 IH singlet, vinyl proton). The enol ether III was hydrolysed in the usual manner to the correspondin, carboxylic acid (III, R'=H). The acid III (R*=H) was reduced with sodium borohydride in isopropenol and, after acidification, was worked up to give a mixture of products from which a,@n.saturated ketone IV was isolated (C20H3404; eq. wt. 32g;u-1726, 1670, 1620 cm -l; x ma 228nqr (3.97); n.m.r. 0.85d 3~ terminal methyl 4 , 3.95,) lH, carbinolic, 6.04 and 6.63 lH each vinyl protons. The ketone IV was then reduced with sodium borohydride and iso-

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