upon Tyne NEI 7RU As a result of methylation, benzoylation, and other chemical experiments, as well as of studies of the conversion into melanin of samples of dopamine specifically labelled with deuterium at each of the a-, p-, 2-, 5-, and 6-positions (separately), a preliminary outline structure is put forward to represent autoxidative dopamine-melanin. This melanin differs considerably from autoxidative dopa-melanin ; in particular, it is suggested that N-C polymeric linkages may be important, and that more uncyclised side chains are present than in dopa-melanin.
upon Tyne NEI 7RU (~)-3,4-Dihydroxyphenyl[~arbo~y-~~C]alanine was converted into melanin, which was oxidised to give pyrrole-2,3,5-tricarboxylic acid, and also decarboxylated. The specific activities of the precursor, the melanin, the acid, the decarboxylated melanin, and the carbon dioxide evolved during the decarboxylation were compared. From the results it was possible to assess approximately the fractions of the polymer units which are ( a ) uncyclised amino-acid units, ( 6 ) carboxylated indole and indoline units, and (c) carboxylated pyrrole units. From the results of methylation experiments the relative proportions of units in the quinonoid and phenolic states were deduced.
The acids named in the title weresynthesised. In the case of pyrroles already containing an ester group, a carboxylic function can be introduced by use of phosgene, but better by use of oxalyl chloride; an acetic ester group can be introduced by use of diazoacetic ester. Some pyrroles containing carboxy-or ester groups are N-methylated by diazomethane.
Durch Kondensation des Aldehyds (I) mit dem Diester (II) bei pH 9‐10 wird das Pyrrol (III) in 13,5%iger Ausbeute erhalten, das mit Phosgen und anschlieβende Reaktion mit Äthanol in den Triester (IV) überführt werden kann (35 %), mit Oxalylchlorid entstehen entsprechende Glyoxylester (V) (80%).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.