Barton aspartate

Hexenyl radicals cyclize to cyclopentylmethyl radicals (see Volume 4, Chapter 4.2). Thus radical decarboxylation of 6-heptenoic acids, by whatever means, usually results in die formation of five-mem-v beied rings. Although this fact had been appreciated previously it is only recendy, widi the advent of the 0-acyl thiohydroxamates, that it has been exploited from a syndietic point of view. An example is provided by the synthesis of bicyclo[4.3.0]proline derivatives from aspartic acid carried out by the Barton group (equation 51). It will be noted that activation of die C—C double bond acting as a radical trap is not necessary in these intramolecular reactions. 

Najlerahim A, Harrison PJ, Barton AJL, Heffernan J, Pearson RCA (1990) Distribution of messenger RNAs encoding the enzymes glutaminase, aspartate aminotransferase and glutamic acid decarboxyla.se in rat brain. Mol Brain Res 7 317-333. 

Side-chain halogenated amino acid derivatives are reduced, deuterated, allylated and alkylated with stannanes and related reagents in free-radical processes [53]. Other side-chain functional groups may also be manipulated to produce amino acid radicals [8, 54-58], and, in particular. Barton decarboxylation of aspartate and glutamate derivatives has been applied in this manner (Scheme 8) [55]. Related procedures have been developed to generate amino acid radicals by dehydrox-ylation of hydroxy amino acid derivatives [56]. Hydroxy amino acid derivatives may also be converted to nitrate esters, from which the corresponding alkoxy radi-... 

Fiser A., Simon I., Barton G.J. (1996) Conservation of amino acids in multiple alignments aspartic acid has unexpected conservation. FEES Lett. 397 225-229. 

The Barton-Zard reaction found its application in the synthesis of LY2059346, a positive allosteric modulator of the a-amino-3-hydroxyl-L-aspartate (AMPA) receptor as a potential treatment of neurological and psychiatric disorders. ... 

Self-catalyzed transesterification with 2-dimethylaminoethanol in DMF has been found effective in cleaving protected peptides from the Mer-rifield resin, in the absence of side-chain benzyl ester protecting groups (Barton et al., 1973). This mild, virtually racemization-free procedure may prove extremely useful for fragment condensation because it yields N-Z-and iV-Boc-protected peptides. Since the reagent, 2-dimethyl-amino-ethanol, specifically cleaves of the benzylic ester group, the benzyl esters of glutamic acid and aspartic acid, if present, will also be hydrolyzed (Barton et al., 1973 Savoie and Barton, 1974). 

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