Prostaglandins conjugate addition

Alkenylcuprates bearing a stereogenic center at the y-position were prepared and used for the synthesis of prostaglandin derivatives. Thus, the conjugate addition of 1 to chiral 2 followed by protonation gave 3 with very high diastereoselectivity623,81. 

Schlessinger and coworkers described a conjugate addition of enolate species to ketene dithioacetal monoxides (equation 357). Some of the products obtained were elaborated to dihydrojasmone , prostaglandins and rethrolones . 

The reaction between trialkylboranes and enones has found some interesting synthetic applications. An example is the preparation of prostaglandin precursors from exo-methylene cyclopentanone, generated in situ from a Mannich base. After dehydrogenation, a second conjugate addition of tri-octylborane was used to introduce the w-chain (Scheme 25) [70]. 

Scheme 10 Vitamin Bi2-mediated cyclization and conjugate addition to prostaglandin PGF2o .

Irrespective of the stereochemistry of the ot,p-enones, lithium alkenyltrialkylalanates, e.g. (28) and (29), obtainable by treatment of alkenylalanes with methyllithium (or n-butyllithium), are also excellent 1,4-conjugate alkenyl transfer reagents. The cornerstone of a general prostaglandin synthesis, as exemplified in Scheme 6, employs the alanate conjugate addition process exclusively.13... 

Scheme 12.3. Synthesis of prostaglandin Et using a three-component conjugate addition/enolate trapping on cyclopentenones, by Noyori and co-workers [10], TBS = t-butyldimethylsilyl, THF = tetrahydrofuran,...

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