Conjugated esters

Recently, chloromethylated benzocoumarin 11c, hydroxylmethylated benzocou-marin 12, and chloromethylated coumarin 13 were used in the efficient preparation of several fluorescent ester conjugates of /V-benzyloxycarbonyl-neurotransmitter amino acids, such as p-alanine, tyrosine, 3,4-dihydroxyphenylalanine (DOPA), glutamic acid, and y-aminobutyric acid (GABA) [39, 40],... 

Miyamoto, J., H. Kaneko, and Y. Takamatsu. 1986. Stereoselective formation of a cholesterol ester conjugate from fenvalerate by mouse microsomal carboxyesterase(s). Jour. Biochem. Toxicol. 1 79-94. 

In addition, three types of lipophilic conjugates have been found in pyrethroid metabolism studies (Fig. 4). They are cholesterol ester (fenvalerate) [15], glyceride (3-PBacid, a common metabolite of several pyrethroids) [16], and bile acid conjugates (fluvalinate) [17]. It is noteworthy that one isomer out of the four chiral isomers of fenvalerate yields a cholesterol ester conjugate from its acid moiety [15]. This chiral-specific formation of the cholesterol ester has been demonstrated to be mediated by transesterification reactions of carboxylesterase(s) in microsomes, not by any of the three known biosynthetic pathways of endogenous cholesterol esters... 

Sung, P., Prakash, S., and Peakash, L. Stable ester conjugate between the Saccharomyces cerevisiae RAD6 protein and ubiquitin has no biological activity. J. Mol. Biol. 1991, 223, 745-49. 

Recent developments involve utilization of cyclodextrins that are absorbed only in minor quantities in the small intestine but are fermented by the colonic bacteria. In a recent study [56,57], the use of biphenyl acetic acid conjugates of P-cylcodextrins was described. The ester conjugate released the drug preferentially when incubated with rat cecal contents, and almost no release was observed on incubation with the contents of the stomach or the small intestine. 

Plant. Degrades in plants to N-glucoside, glucose ester, conjugates, and insoluble residues (Ashton and Monaco, 1991). 

Geraldes, C. F.,A. D. Sherry, W. P. Cacheris, K.-T. Kuan, R. D. Brown, S. H. Koenic, M. Spillers. 1988. Number of inner-sphere water molecules in feteland Ei + complexes of DTPA-amide and -ester conjugates. Magn. Reson. MedB 191-199. 

Bowers, G. D. Higton,D. M. Manchee, G. R. Oxford,X Saynor,D. A. 1991. Thermospray liquid chromatography-mass spectrometry for the characterisation of sulphate ester conjugates. J. Chromatogr.,554,175-180. 

The photolysis of phenyl benzoate 8.88 is an example of the photo-Fries rearrangement, in which the acyl radical is created close to a phenoxy radical 8.89. The C—O bond is weakened by the presence of an electron in the n orbital of the ester conjugated system. The radical coupling then shows the usual selectivity for C—C bond formation, with the para selectivity in line with the coefficients of the SOMO of the phenoxy radical (see page 291). 

Treatment of a,p-unsaturated esters with triethylsllane in benzene in the presence of catalytic amounts of RhCl(PPh3)3 at room temperature yields the corresponding saturated esters. Conjugated diene esters are reduced to the p,-y- or -y,8-unsaturated esters, depending upon their substitution pattern (Scheme... 

Conjugate addition of a silylcuprate reagent (34) to the a,(3-unsaturated acid amide or ester of a pertinent chiral amine or alcohol, respectively, is an alternative route to (3-silyl amides and esters. Conjugate addition of a cuprate reagent to a P-silyl acrylamide also gives a chiral P-silyl amide. The diastereomeric excess of the newly produced chiral center is fairly high, as summarized in Scheme 14." ... 

Lateral metallation at C-2(a) of l-/ftt-butoxycarbonyl-2-methylimidazoline 709 (Scheme 173) with r f-BuLi results in the formation of a bright yellow lithiated intermediate that reacts with alkyl halides, diphenyldiselenide, and phosphoryl chlorides to give 710. In the case of reaction with esters, the conjugated ketones 711 are formed <2000T2061>. In the case of acylation with esters, conjugated enamino-ketones were the tautomer isolated. Further alkylation is also possible under similar conditions, to give 712. 

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