Steroids CCCXII. A new synthetic route to bisdehydrodoisynolic acids.

Ab → Abc → Abcd

“…The latter, then was cyclized by reaction of the corresponding acid chloride with stannic chloride to give the tricyclic keto ester 125. Subsequent hydrogenolysis of the keto group, followed by Several other syntheses of bisdehydrodoisynolic acid have been described in the literature [97][98][99][100][101][102][103]. Gay and co-workers [97][98][99][100], starting with the ketone 123, synthesized 127 (R = H) in poor yield.…”

Ab + D → Abd → Abcd

“…It was cyclized in 93% yield to the 16-oxasteroid 111, which was dehydrogenated to the corresponding aromatic ring B analog (80% yield) [98]. The latter was converted to the carbocyclic steroid 112 in 60% yield by the action of methylenetriphenylphosphorane [99].…”

“…The latter was converted to the carbocyclic steroid 112 in 60% yield by the action of methylenetriphenylphosphorane [99]. The D ring of 111 is an enol lactone; it was hydrolyzed with sodium hydroxide, and the resulting keto acid converted to cis-bisdehydrodoisynolic acid methyl ether, thereby confirming the carbon skeleton [98]. An attempt to synthesize a B-seco intermediate suitable for the preparation of heterocyclic steroids was initiated with the reaction of 113 with 2-methyl-l,3-cyclopentanedione.…”

A new phosphorane obtained from dimethylketene

“…Excess methyl iodide and Ia reacted at room temperature in several days to give a near quantitative yield of VIII for which the pmr spectrum (benzene) shows peaks of appropriate intensities at 1.28 (singlet, -butyl group), 1.51 and 2.07 (doublets, /Hp = 2.5 and 3.0 Hz, vinyl (7) The hydrolysis of III would be expected to yield 1 mole each of isobutyric acid and the ketophosphonate IV. However, IV would not survive the hydrolysis conditions,8 but would react further with water to give isobutyric acid, methanol, and phosphorous acid.…”