Catechins acetylated

Alkaloids produce variously colored chromatogram zones (yellow, pink, brown, purple) on a light background [2]. Indole and the catechins appear red [4, 5, 8, 9, 12, 16]. If the catechins are acetylated it is necessary to heat to 105 °C for 5 min after treatment with the reagent [8]. Lysergic acid derivatives should also be heated to 75 °C for 5 min. 

F-A or A -F adducts (epi)Catechin-malvidin 3-0-glc (epi)Catechin-peonidin 3-0-glc (epi)Catechin-petunidin 3-0-glc (epi)Catechin-malvidin 3-0-glc (epi)Catechin-malvidin 3-0-(6-0-acetyl)glc (epi)Catechin-malvidin 3-0-(6-0-/ -coumaroyl)glc (epi)Catechin-delphinidin 3 - O-glc (epi)Catechin-cyanidin 3-O-glc (epi)Catechin-petunidin 3-O-glc (epi)Catechin-peonidin 3-O-glc... 

The synthetic protocol (Scheme 11.2) toward the flavan-3-ol permethylaryl ethers is based upon the transformation of rc7ro-chalcones into 1,3-diarylpropenes. These compounds are then subjected to asymmetric dihydroxylation to give diarylpropan-l,2-diols that are used as chirons for essentially enantiopure flavan-3-ols. The protocol is demonstrated in Scheme 11.2 for the synthesis of the tetra-(9-methyl-3-(9-acetyl derivatives 61a, 61b, 62a, and 62b of (-l-)-catechin (2), (—)-e 7-catechin, (—)-epicatechin (3), and (+)-e 7-epicatechin (4). ... 

Simultaneous deprotection and cyclization of diols 60a and 60b with 3 M HCl in MeOH followed by acetylation yielded the 2,3-trans- ( 50%) (61a and 61b) and for the first time 2,3-cw-flavan-3-ol methylether acetate derivatives ( 20%) (62a and 62b) in excellent enantiomeric excesses (>99%). The optical purity was assessed by H NMR using [Eu(hfc)3] as chiral shift reagent. The absolute configuration of the derivatives of the tram- and cii-flavan-3-ol derivatives was assigned by comparison of CD data with those of authentic samples in the catechin or epicatechin series flavan-3-ols. Thus, the absolute configuration of the flavan-3-ol methyl ether acetates confirms the assigned configuration of the diols as derived from the Sharpless model. 

Evidence in wine. The procyanidin dimer-vinylpyranomalvidin-3-glucoside and its 7)-coumaroyl ester have been isolated from Port wine and completely characterized by ESl/MS and NMR (Mateus et al. 2003b). Later, the catechin-vinylpyrano derivatives of petunidin, peonidin and malvidin-3-glucosides, malvidin-3-(6-acetyl)-glucoside and peonidin and malvidin-3-(6-7)-coumaroyl)-glucosides, have also been... 

In an acid dilute alcohol medium, comparable to wine (pH 3.2), de Freitas (1995) showed that the carbocation formed from procyanidin B3 (Figure 6.23) could easily react with a nucleophilic compound, such as ethanethiol. The 4-o -ethylthioflavan-3-ol derived from (-l-)-catechin has been isolated and synthesized (Figure 6.24). Its structure has been formally established by NMR of the proton and Ci3 after acetylation. Thiolysis is a standard technique using various thiols (toluene a-thiol, benzene thiol) to study procyanidic oligomer structures. This... 

Flavonoid acetates and methyl ethers have been separated by WEmoES and Toribio [236] using solvent II (Table 166). Catechin-resorcinol condensation products in particular can be resolved in this way [236]. Catechin acetate diastereoisomers and the acetates of oUgomeric flavonoid tannins such as the acetates of dicatechin and anhydro-catechin can be thus detected with certainty [56]. The acetates of the more highly condensed compounds remain at the start point. Plant extracts containing catechins and flavonoid tannins are best acetylated initially by 15 h treatment with acetic anhydride/absolute pyridine at room temperature. Solvent II or chloroform-ethyl acetate (90 + 10) can be used with silica gel columns for preparative separation of such mixtures. 

The structure of penta-O-acetyl-catechin is an interesting example of problems encountered in definition of the conformation of these compounds. In the crystal state, the heterocyclic ring is in a reverse half-chair conformation with both the 5-ring and 3-acetoxy substituents in axial positions (120). However, the heterocyclic ring proton coupling constants 2,3 = h,4a - and... 

Fronczek F R, Gannuch G, Tobiason F L, Shanafelt H A, Hemingway R W, Mattice W L 1985 Preference for occupancy of axial positions by substituents bonded to the heterocyclic ring in pen-ta-0-acetyl-( + )-catechin. J Chem Soc Perkin Trans II 1383-1386... 

Low temperature H NMR studies (111) showed that the E A ratio for catechin (14) and epicatechin (11) were 62 38 and 86 14 respectively. Acetylation of the 3-hydroxy group stabilised the A-conformation of catechin and changed the ratio to 48 52. 

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