The first synthesis of carminic acid (7 beta-D-glucopyranosyl-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid) is described. Selective C-glycosylation at the 7-position of ethyl and benzyl 3,5,8,9,10-pentamethoxy-1-methylanthracene-2-carboxylates with 2,3,4,6-tetra-O-benzyl-1-trifluoroacetyl-alpha-D-glucopyranose afforded intermediates which were oxidised to ethyl and benzyl 3,5,8-trimethoxy-1-methyl-9,10-dioxo-7-(2',3',4',6'-tetra-O-benzyl-beta-D-glucopyranosyl)-9,10-dihydroanthracene-2-carboxylate respectively. The benzyl compound was hydrogenolysed and the ethyl analogue hydrogenolysed and hydrolysed to give the same product, which was tetraacetylated and demethylated to afford 6-deoxycarminic acid tetraacetate, 3,5,8-trihydroxy-1-methyl-9,10-dioxo-7-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)-9,10-dihydroanthracene-2-carboxylic acid. The pentamethoxy intermediates were obtained from 2-chloronaphthazarin by Diels-Alder addition to 3-alkoxycarbonyl-2,4-bis(trimethylsiloxy)penta-2,4-dienes to give alkyl 6-deoxykermesates. Methylation afforded the corresponding trimethyl ethers, which by reductive methylation gave the required pentamethoxy compounds. By known steps 6-deoxycarminic acid tetraacetate was converted into the 5,8,9,10-bisquinone, acetoxylation of which gave carminic acid octaacetate. Acidic hydrolysis afforded carminic acid

Synthesis of carminic acid, the colourant principle of cochineal / P. Allevi, M. Anastasia, S. Bingham, P. Ciuffreda, A. Fiecchi, G. Cighetti, M. Muir, A. Scala, J. Tyman. - In: JOURNAL OF THE CHEMICAL SOCIETY. PERKIN TRANSACTIONS. I. - ISSN 0300-922X. - :3(1998), pp. 575-582.

Synthesis of carminic acid, the colourant principle of cochineal

P. Allevi
Primo
;
M. Anastasia
Secondo
;
P. Ciuffreda;G. Cighetti;
1998

Abstract

The first synthesis of carminic acid (7 beta-D-glucopyranosyl-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid) is described. Selective C-glycosylation at the 7-position of ethyl and benzyl 3,5,8,9,10-pentamethoxy-1-methylanthracene-2-carboxylates with 2,3,4,6-tetra-O-benzyl-1-trifluoroacetyl-alpha-D-glucopyranose afforded intermediates which were oxidised to ethyl and benzyl 3,5,8-trimethoxy-1-methyl-9,10-dioxo-7-(2',3',4',6'-tetra-O-benzyl-beta-D-glucopyranosyl)-9,10-dihydroanthracene-2-carboxylate respectively. The benzyl compound was hydrogenolysed and the ethyl analogue hydrogenolysed and hydrolysed to give the same product, which was tetraacetylated and demethylated to afford 6-deoxycarminic acid tetraacetate, 3,5,8-trihydroxy-1-methyl-9,10-dioxo-7-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)-9,10-dihydroanthracene-2-carboxylic acid. The pentamethoxy intermediates were obtained from 2-chloronaphthazarin by Diels-Alder addition to 3-alkoxycarbonyl-2,4-bis(trimethylsiloxy)penta-2,4-dienes to give alkyl 6-deoxykermesates. Methylation afforded the corresponding trimethyl ethers, which by reductive methylation gave the required pentamethoxy compounds. By known steps 6-deoxycarminic acid tetraacetate was converted into the 5,8,9,10-bisquinone, acetoxylation of which gave carminic acid octaacetate. Acidic hydrolysis afforded carminic acid
CARMINIC ACID ; C-GLUCOSIDES ; C-GLUCOSIDATION : DIELS-ALDER ADDITION
Settore BIO/10 - Biochimica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/184225
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