Corey lactol

Corey lactol, 4 Cormethasone acetate, 194 Cormethasone acetate, 196 Cortisone, 176, 179 Cortivazol, 191 Cotinine, 235 Curare, 162 Cgclacillin, 439 Cgclazocine, 327 Cyclic adenosine monophosphate, see CAMP Cgclobendazole, 353 Cyclopropanation, 32, 166, 168, 174. 223, 297 Cgheptamide, 222 Cypenamine, 7 Cyprazepam, 402 Cyprolidol, 31 Cyproquinate, 368 Cyproterone acetate, 166 Cyproximide, 293... 

In addition to its other properties, interest in the potential use of the vasodilative properties of prostaglandin El, alprostadil ( ), has led to several conceptually different syntheses.For this purpose, the classic Corey process has to be modified by reversing the order of addition of the side chains to allow for convenient removal of the unwanted double bond in the upper side chain. For example, Corey lactone is protected with dihydropyran (acid catalysis), reduced to the lactol with diisobutyaluminum hydride, and then subjected to the usual Wittig reaction to give intermediate This is... 

A stable tetrahedral intermediate is more likely in the reduction of lactones, and DIBAL is most reliable in the reduction of lactones to lactols (cyclic hemiacetals), as in E.J. Corey s synthesis of the prostaglandins. The key step, the hydride transfer from Al, is shown in the green frame. 

A stable tetrahedral Intermediate Is more likely In the reduction of lactones, for the same reasons that cyclic hemiacetals are more stable than acyclic ones. DIBAL Is most reliable In the reduction of lactones to cyclic hemiacetals (also known as lactols), as In this reaction from E. J. Corey s synthesis of the prostaglandins. 

Allenyl analogues (182) and (183) of the F, - and E-series have been synthesized by the Syntex group starting from the lactol intermediate (9) from Corey s PG synthesis (Scheme 39). ... 

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