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Total synthesis of steroidal derivatives : synthesis of hydrochrysene analogues and related compounds. By, Arnold William

Abstract

A sequence leading to the total synthesis of cis-syn-cis-dodecahydrochrysene and cis-octahydrochrysene derivatives is described. The synthesis employs the Robinson-Mannich base reaction and the Michael reaction to construct the tetracyclic skeleton. Condensation of 6-methoxy-2-tetralone with 1-diethylamino-3-pentanone methiodide affords an isomeric mixture of tricyclic ketones. This mixture is then condensed with methyl vinyl ketone to yield 1β,6-dimethyl-6-hydroxy-2,3-(2'-methoxy-7',8'-dihydro-6',5'-naphtho)-Δ² -bicyclo [3.3. 1] nonene-9-one (IV). By appropriate modifications this compound can then be utilized for the synthesis of a variety of hydrochrysene analogues. Oxidation of dodecahydrochrysenes with t-butyl chromate solution is found to be dependent on the stereochemistry of the molecule. Whereas trans-anti-trans-2-methoxy-8β -acetoxy-10a-methyl-4b, 5,6,6a, 7,8,9,10,10a,10b,11,12-dodecahydrochrysene (XVIII) gives the 12-keto derivative XIX, cis-syn-cis-2-methoxy-8α-acetoxy-10a-methyl-4b,5,6,6a,7,8,9,10,10a,10b,11,12-dodecahydrochrysene (XVII) yields cis-2-methoxy-8α -acetoxy-5-keto-10a-methyl-5,6,6a, 7,8,9,10,10a-octahydrochrysene (XXIV). In the latter reaction, t-butyl chromate is superior to chromium trioxide as an oxidizing agent. Nuclear magnetic resonance spectra are found to be invaluable for the purpose of characterization of these rather complex molecules.

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