D-cysteine, methyl ester

C4-Chiral thiazolidine-2-thiones were prepared by condensation, as, for example, (4/ )-methoxycarbonyl-l,3-thiazolidine-2-thione [(4/ )-MCTT] (I) from L-cysteine methyl ester hydrochloride and carbon disulfide (CSj) in the presence of triethylamine (EtjN) in CH2CI2 at room temperature (Scheme 1) (82TL201 85JOC4072). The (4S)-enantiomer was similarly synthesized by using D-cysteine methyl ester hydrochloride (85CC1419). 

New cyclic methylseleno imino compounds were synthesized from (4/ )-MCTT (I) or D-cysteine methyl ester (154) (Scheme 28) (86JOC4737). 

The second route [91] was developed by Baldwin and used aminoacid derivatives as chiral precursors. The homopenam intermediate 163 was prepared as previously described in section 3.1.1 by condensation of L-aldehyde 161 with D-cysteine methyl ester (Scheme 49). The unsaturation was introduced into the thiazolidine ring by treatment of 163 with benzoyl peroxide, followed by base-induced elimination of benzoic acid. 

The OV-17 phase has been found to give improved separation of the diastereoisomerlc pertrimethylsilylated methyl 2-(polyhydroxy-alkyl)thiazolidine-(ilR)-carboxylates formed from enantiomeric pairs of nine aldoses after reaction with L-cysteine methyl ester (c.f. Vol.20, p.2il8). Although each pair of sugar enantiomers gave separate peaks, those from different sugars, e.g., D-xylose and L-arabinose, sometimes co-eluted, ... 

N.m.r. results indicate that the square-planar complexes formed between Ni" and L-cysteine or its methyl ester appear to have some (d-d)n character to the Ni—S bonds." °... 

Icmt catalyzes the methyl esterification of the prenylated cysteine residue after Reel has proteolyzed the -CaaX-containing proteins. The first step in identification of the minimal substrate for Icmt was through identification of AFC (Figure 9.2) as described above. Interestingly, farnesylcys-teine (FC), which is devoid of the acetyl substitution, was not a substrate but did possess some activity as an inhibitor [51], suggesting that the free amine of FC requires modification for catalytic turnover. Alterations in the stereochemistry about the FC backbone also appeared to be detrimental to substrate activity. The stereoisomer, d-AFC, was not a substrate for Icmt but was a modest mixed-type inhibitor of the enzyme. AFC-methyl ester (AFC-Me) was also reported to be a mixed-type inhibitor with respect to both l-AFC and -adenosylmethionine (SAM), the methyl donor, with Ki values of 41 and 73 pM, respectively [52,53] The farnesyl homocysteine homolog of AFC is not a substrate for the enzyme however, the racemic DL-homocysteine farnesyl derivative is in fact a weak inhibitor [40]. Similar to the results with racemic prenylcysteine, these data demonstrate that the linker between the carboxylate and thioether moieties is critical for substrate activity. 

The reactions of -mercaptoethylamine, L-cysteine, and D-penicillamine, and their derivatives, with a-haloketones represent an important synthetic route to dihydrothiazines. " For example, the methyl esters of L-cysteine and D-penicillamine reacted with 3-bromo-2-oxopropionic add... 

In human nutrition, free amino acids play an important role in aromatisa-tion, as flavour enhancers, and as sweeteners. Monosodium glutamate, in concentrations of 0.1-0.4%, is probably the most prominent flavour enhancer for spices, soups, sauces, meat and fish. (L)-Cysteine amplifies the flavour of onions. Glycine is used to mask the aftertaste of saccharin. Whereas (L)-amino acids may taste slightly bitter, the (D)-enantiomers have a sweet taste. This is in general also true for the corresponding di- and oligopeptides - except for the methyl ester of (L)-aspartyl-(L)-phenylalanine (Aspartame). 

S Additional information <9, 15, 17, 18, 21, 24, 30, 33, 35> (<18> activity is regulated by light [28] <30> D-aspartate, L-glutamate and -alanine are inactive as substitutes for L-aspartate in the forward reaction, in the reverse reaction ADP cannot be replaced by AMP, UDP, GDP or IDP [1] <17> aspartokinase III, o-isomers of the derivatives of aspartic acid, including D-aspartate cr-benzyl ester and o-aspartate /)-hydroxamate are not substrates regardless of whether the a- or the -carboxyl group is derivatized, L-cysteine sulfinate and 2-methyl-DL-aspartate are no substrates... 

Chiral 2-thiazolidinethiones, e.g., 40, prepared from cysteine esters by the reaction with carbon disulfide23, are used for the enantiotopic differentiation of methylene groups (Section C.). Similarly, carbon disulfide reacts with amino alcohols such as (5)-2-amino-J-butanol or (S)-2-amino-3-methyl-1-butanol (valinol) to give the 2-thiazolidinethiones (S)-ETT 42 and (S)-IPTT 4124 which have been used as auxiliaries (after Y-acylation with carboxylic acids and dicyclo-hexylcarbodiimide) in acylimonium ion cyclizations (Section D.I.4.5.). 

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