Browsing by Author "Chew, Steven"

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Nitration of some derivatives of vanillic and veratric acids
(Te Herenga Waka—Victoria University of Wellington, 1981) Chew, Steven
The behaviour of methyl 4 - acetoxy - 3 - methoxybenzoate and methyl 3,4 - dimethoxybenzoate with nitric acid have been examined and compared. With methyl 4 - acetoxy - 3 - methoxybenzoate, only the 2 - nitro product was observed while with methyl 3,4 - dimethoxybenzoate, the 6 - nitro product was isolated. This has been rationalised by invoking a co-ordination mechanism. The effect of the nitration medium was also studied. Studies of the nitration of some methyl esters of vanillic acid in which the 4 - hydroxyl group had been esterified with various acyl groups have also been carried out, and again, the products of nitration in the 2 - position were found to predominate.
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Synthetic Approaches to Anthracyclinones from Carbohydrates
(Te Herenga Waka—Victoria University of Wellington, 1985) Chew, Steven
The Diels-Alder reaction of a cyclic carbohydrate enone with o-xylylenes derived from 1,2-bis (bromomethyl)benzene and 2,3-bis (bromomethyl)naphthalene by treatment with zinc powder under ultrasound irradiation afforded tri- and tetra-cyclic products which were converted into optically pure, functionalised hexahydro-anthracene and -naphthacene derivatives. The latter compounds have the carbon framework, A-ring functionality and stereochemistry similar to those of some anthracyclinones hence a potentially novel route to these pharmaceutically important compounds has been opened. The synthesis of a tricyclic analogue of α1-rhodomycinone with the required A-ring functionality was accomplished by the reaction of a hexahydro-anthracene-based ketone with methyllithium but attempts to achieve the B-ring functionality were not successful. The reaction of levoglucosenone with o-xylylene gave three products - an adduct and two novel tertiary alcohols which were formed by a nucleophilic attack on the carbonyl group.