A study of the oxidation of some phenolic 1,2,3,4-tetrahydroisoquinoline-1-carboxylic acids

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Tinley, E.J., 1977. A study of the oxidation of some phenolic 1,2,3,4-tetrahydroisoquinoline-1-carboxylic acids. PhD, Nottingham Trent University.

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Abstract

Following the publication of a report on the anodic oxidation of 6-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acids a range of such compounds with differing alkyl substituents at the C-1 position was synthesised and incubated with enzymes known to oxidise phenolic molecules. It was found that oxidative decarboxylation to the corresponding 3,4-dihydroisoquinoline occurred, the reactions being followed spectrophotometrically, and although a competing reaction was also observed an estimate of the enzyme kinetics (Kia and V) was made. This reaction is additional evidence in favour of the Hahn postulate implicating isoquinoline-1-carboxylic acids in the biogenesis of isoquinoline alkaloids, and also illustrates the similarities between enzymatic and electrochemical oxidations.

As a consequence of the reported oxidative decarboxylation of phenolic N-protected acids to quinonoidal species, two N-trifluoroacetyl-6-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acids, having nucleophilic benzyl substituents were synthesised and oxidised by electrochemical, enzymatic and chemical means, in order to study their possible intramolecular coupling to aporphine and cularine alkaloids. Synthesis of the target alkaloids by conventional methods was also undertaken. Similarly the possibility of intermolecular coupling of an external nucleophile to the oxidised form of N-trifluoroacetyl-1-methyl-6-hydroxy-V-methoxy-1,2,3,4-tetrahydroisoquinoline-l-carboxylic acid was investigated, both electrochemically and enzymically.

An unsuccessful synthesis of β,β-dimethyl-35-trimethoxyphenylpyruvic acid was undertaken in an attempt to prepare the appropriately substituted α,α-dimethyl isoquinoline-1-carboxylic acid.

Reaction of 1-(3,4,5-trimethoxybenzyl)-6-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid with trifluoroacetic anhydride in pyridine gave rise to an anomalous product, which was identified as a fluorine containing dihydroprotoberberine.

The enzymatic oxidation of corypalline was investigated using fungal laccase and horseradish peroxidase; both enzymes were found to be capable of effecting phenol oxidative coupling to give the carbon- carbon linked dimer.

Item Type:

Thesis

Creators:

Tinley, E.J.

Date:

1977

ISBN:

9781369313918

Identifiers: