ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Total Synthesis of Betalainescis-4-Oxo-2,6-piperidinedicarboxylic acid dimethyl ester (10) was transformed (44%) into the semicarbazone of 2,3-dihydrobetalamic acid dimethyl ester (13/14) by a modified Horner-Wittig reagent 12. Oxidation of 13/14 afforded 41% of a mixture of stereoisomers of betalamic-acid-dimethyl-ester semicarbazone (4), key intermediate for the synthesis of betalaine pigments. The utility of 4 in this respect was demonstrated on a small scale by its conversion to the dimethyl ester of indicaxanthine (9, 11%) and to the trimethyl ester of betanidine (7, 87%). Hydrolysis of 7 gave betanidine (6).We further describe the synthesis of the trimethyl ester of an oxidized form of betalamic acid (20/21) as well as model condensation reactions on the carbonyl group of cyclohexanone, cis-4-oxo-2,6-diphenylpiperidine (23) and its N-formyl derivative 27.Reaction of 4-oxo-1,2,3,4-tetrahydro-2,6-pyridinedicarboxylic-acid dimethyl ester (40) with acetic anhydride or with triethyloxonium tetrafluoroborate resulted in O-acylation or in O-alkylation along with dehydrogenative aromatization to yield the derivatives 39 or 42, respectively, of chelidamic acid.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19770600240
