Alcohols, acetylation tertiary hydroxy groups

Dregeanin and two y-lactones (103) obtained from it on hydrolysis, to be described further below, show an i.r. maximum near 1790 cmwhile D5 and the two rohituka substances show maxima at 1775 cm The reason for this is not known. It is possible that D5 may have the isomeric structure (104) with a 8-lactone and a tertiary hydroxy group. The arguments against this alternative structure are that all six of these compounds show a C-4 resonance at about 8 90, distinct from any other dregeanin derivative, which has been explained on the basis that C-4 is included in a y-lactone ring, (755). Also D5 and the rohituka compounds show a shift in the 2H-29 resonance from ca. 8 3.8 (s) to 8 4.1,4.3 (d, J = 12 Hz.) on acetylation, which is explained as due to the acetylation of a primary alcohol. Prieurianin has the C-4 resonance at 8 84.6, rohitukin, a 7,29 lactone, at 8 79.4 ppm. 

Cholesteryl acetate dibromide is first prepared by the acetylation of chloesterol and its subsequent bromination. This on oxidation with chromium-6-oxide reduces the 8-carbon side chain at C-17 to a mere CO moiety, which on reduction followed by hydrolysis yields dehydroepiandro-sterone. The resulting product on acetylation protects the acetyl moiety at C-3 and treatment with sodium propoxide introduces a hydroxy group at C-17. Benzoylation followed by mild hydrolysis causes the reappearances of free OH moiety at C-3 and a benzoxy function at C-17. Oppeanauer oxidation cuased by refluxing the resulting secondary alcohol with aluminium tertiary butoxide in excess of acetone affords a ketonic function at C-3, which upon hydrolysis in an alkaline medium yields the official compound. 

Addition of l,3-bis(methylthio)allyllithium to aldehydes, ketones, and epoxides followed by mercuric ion-promoted hydrolysis furnishes hydroxyalkyl derivatives of acrolein5 that are otherwise available in lower yield by multistep procedures. For example, addition of 1,3-bis-(methylthio)allyllithium to acetone proceeds in 97% yield to give a tertiary alcohol that is hydrolyzed with mercuric chloride and calcium carbonate to saturated aldehyde.8 Similarly, addition of l,3-bis(methylthio)allyl-lithium to an epoxide, acetylation of the hydroxyl group, and hydrolysis with mercuric chloride and calcium carbonate provides a 5-acetoxy-a,/ -unsaturatcd aldehyde,6 as indicated in Table I. Cyclic cis-epoxides give aldehydes in which the acetoxy group is trans to the 3-oxopropenyl group. 

Further analysis indicated that porphyroxine contained one —OMe group, and that it was a tertiary base readily giving quaternary salts [7]. An acetyl-derivative was prepared showing the alkaloid to be an alcohol as the free hydroxy-compound was alkali-insoluble. The presence of a carbonyl group in the molecule was demonstrated by the preparation of an oxime, semicarbazone, and phenylhydrazone. Methylporphyroxine was obtained by treating the quaternary salts with alkali, and methyltetrahydroporphyroxine by sodium amalgam reduction of porphyroxine methomethylsulphate. These derivatives also yielded oximes [7]. 

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