Tartaric conjugates

However, in view of quantities consumed by other populations, wines could make a significant contribution for tartaric acid conjugates and grapes and grape juice for caftaric acid, respectively. Lettuce is the major source of chicoric (dicaffeoyltartaric) and caffeoylmalic acid (up to 3 mg/100 g), but endive may have twice the concentration. Spinach is almost certainly the richest source of conjugated p-coumaric acid at some 30-35 mg/100 g [18]. 

Phenolic acids are rarely present as free forms, except in processed food, but occur more frequently as soluble or insoluble esters. These esters are formed with polysaccharides or simple sugars, with quinic acid or other carboxylic acids such as tartaric or shikimic acids [Herrmann, 1989], with other phenolic acids, with lipids [Clifford, 2000], with sterols or glycerol [Clifford, 1999], or with amino acids [Clifford and Knight, 2004], To quinic acid, they can be conjugated as mono-, di-, tri-, and tetra-esters [Clifford, 2000]. The multiple esters can contain the same or different hydroxycinnamic acids. Among the hydroxycinnamic conjugates, caffeoylquinic and di-caffeoylquinic acids... 

The palladium(II)-catalyzed [3,3] sigmatropic rearrangement of the (4.S ,5.S )-diacetate, derived from tartaric acid (entry ll)21 produced only the conjugated (2/ ,7R)-diacetate the other possible conjugated (25,35)-diacetoxy-4,6-diene derivative was not detected. 

Cinchona diimides have also been used to develop a simple colorimetric indicator displacement assay for the determination and chiral discrimination of tartaric acid. Thus, conjugation of 72 with bromophenol blue 73 resulted in the formation of a dark blue complex (A,m lx at 597 nm) that after treatment by an appropriate acid released the protonated form of the indicator with a well-separated absorption maximum at 426 nm. This assay allowed to determine (R,R)-tartaric acid with the detection limit as low as 0.02 mg/ml and efficiently discriminated the enantiomers of tartaric adds,... 

Novel enantiopure C2 symmetric bis(oxazolines) 171 were obtained from tartaric acid and applied in the copper-catalyzed conjugate addition of diethylzinc to chalcone and 2-cydohexenone. The sense of induction was found to depend on the configuration of the stereogenic centers in the oxazoline rings and not in the 1,4-dioxane backbone <05TA2946>. 

Though milder conditions (NaOH, Et20) gave 42 in 86% yield, this was of course racemic. The single enantiomer was made from tartaric acid 47 by conversion into the enone 48, conjugate addition of a lithium cuprate with excellent anti-selectivity 49 and elimination with DBU.14... 

Several simple phenylpropanoids (C6-C3) are produced from cinnamate via a series of hydroxylation, methylation, and dehydration reactions these include p-coumaric, caffeic, ferulic and sinapic acids and simple coumarins. The free acids rarely accumulate to any great extent within plant cells but are usually conjugated to sugars, cell wall carbohydrates, or organic acids (quinic, malic, tartaric, etc.). Lignin and suberin are complex polymers formed from a mixture of simple phenylpropanoids, and will not be considered in the present review. 

Seebach studied the conjugate addition reaction of nitroolefin 10 with butyllith-ium in the presence of the multidentate ligand 11 (accessible from tartaric acid), which yielded the adduct 12 in up to 58% ee (Scheme 4) [18]. 

The efficacies of prolinamide bearing a carbohydrate group on nitrogen, six / -cyclodextrin conjugates with proline, and two with the enantiomers of proline-derived 2-aminomethylpyrrolidine have been reported for aldol reactions in water. The performance of new pyrrolidine-based organocatalysts derived from tartaric and glyceric... 

Tartaric Acid-Derived Quaternary Ammonium Salts Starting from the freely available tartaric acid, Shibasaki et al. designed and prepared a series of diammonium salts by changing the acetal moieties (R and R ), aromatic parts (Ar), and counteranions (X) (Figure 12.11). Screening of the catalyst hbrary identified that catalyst 48a was efficient for the asymmetric alkylation of N-(diphenylmethylene) glycine tert-butyl ester [81] and that the C2-symmetric catalysts 48b, 49, and 50 were efficient for the conjugate addition [82]. 

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