Graduate Thesis Or Dissertation
 

Approaches to the synthesis of polyketides. Vermiculine

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  • An approach to the generation of polyketides was investigated, which involved ozonolysis of 6, 7 cyclopenteno -1> 4, 5, 8 -tetrahydromethoxy- 3-methylnaphthalene (26), to produce what is believed to be polyketide 27. Compound 26 was formed by the following sequence: Die ls -Alder addition of 1, 2 -dim.ethylenecyclopentane and 2 -methoxy- 3-methylbenzoquinone (29) afforded adduct 30 which was reduced with lithium aluminum hydride to diol 31, followed by dehydration with phosphorus oxychloride to 32 and subsequent lithium-ammonium reduction to produce 26. The synthesis of vermiculine (63) was studied. Hagemann's ester was converted to alcohol 113 by the action of isopropenyl acetate and p-toluenesulfonic acid followed by reduction of the resulting mixture with sodium borohydride in aqueous dioxane. Reduction of 113 with lithium aluminum hydride produced diol 115 which was oxidized with manganese dioxide to aldehyde 117. Reaction of 117 with the anion of triethyl phosphonoacetate followed by acetylation of the resulting product (98) gave diester 99. Epoxidation of 99 with m-chloroperbenzoic acid yielded 105, which was hydrolyzed to diol 106 by the action of aqueous perchloric acid. The diol was cleaved with lead tetraacetate in pyridine and ethyl acetate to produce the protected vermiculinic acid 107. Ketalization of 107 with ethylene glycol followed by saponification of the esters yielded hydroxy acid 110. Attempts to cyclize 110 were unsuccessful. A route to the noncyclic dimer was developed starting from 98. Bromoacetylation of 98 followed by an Arbusov reaction with trim.ethylphosphite gave phosphonate 127, which was condensed with aldehyde 117 to afford dimer 128. Epoxidation of 128 with m-chloroperbenzoic acid followed by hydrolysis of the bisepoxide (129) with aqueous perchloric acid produced pentol 130. Lead tetraacetate cleavage of 130 gave the protected vermiculinic acid dimer (131).
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Déclaration de droits
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