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Date of Award

2000

Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)

Department

Chemistry

First Advisor

Paul H. Gross

First Committee Member

James W. Blankenship

Second Committee Member

Donald K. Wedegaertner

Abstract

Prince-type cyclizations were performed with different Lewis acids to select optimal conditions, for the synthesis of a series of 4-chloro-2- phtalimidomethyl 6-methyl tetrahydropyrans and 4-chIoro-2.6- bis(phtalimido-methyl)-tetrahvdropyrans. The total yield for phtalimidomethyl products reached 92%, and for bis-phtalimido compounds 71%. An influence of reagent size and nucleophilicitv on the reaction outcome was observed, and was interpreted in terms of cationic mechanism and complex formation in the transition state. A cyclization step was also used to synthesize bicvclic compounds that can be used as precursors for the synthesis of C-oligosaccandes. Optimized eliminations of hydrogen halide by DBU in presence of LiCl yielded a mixture of 2.6-anhydro-1.3.4.5.7- penradeoxy-l-phtahmido-DA-erythrohepr-3-emto! 5b and 2.6-anhydrol, 3,4,5,7-pentadeoxy-l-phtalimido-D.L-erythrohept-4-enitoI 6b in 79°a yield for the isomeric mixture. Epoxidation of this alkene mixture by a newly developed method with urea-hydrogen peroxide complex and trifluoroaceric anhydride afforded a mixture of epoxy-2-methvl-6- phtalimidomethyl tetrahydropyrans in 92% total yield. Epoxides were cleaved by aq. CF3COOH to give a mixture of dihydroxy-2-methyi-6- phtalimi dome by 1 tetrahydropyrans with an overall yield of 74% from the mixture of 5b/6b. The regioisomers were separated and deprotected by a newly developed method, and were oxidized to produce partially functionalized racemic aminomethyl C-glycopyranosides. One of the isomers was characterized as an N-acetyl-di-O-acetyl derivative and as a NBoc di-O-acetyl derivative, because this isomer was very hygroscopic.

It was also found that transallylation occurred between acetal and homoallylic alcohol during the cyclization step. A new method for the synthesis of homoallylic alcohols from acetals was developed on the basis of this observation. Homoallylic alcohols, l-Benzyloxv-4-penten-2-ol 19. 1- Phenyl-4-pentene-2-ol 18 and BPhtalimido-4-pentene-2-ol 1β were synthesized by a new method with yields of 40%. 61 % and / i % respectively. The as yet unoptimized method allows to synthesize homoallylic alcohols from unstable aldehydes.

Pages

127

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