Serine 3-lactone

Ring Opening of Serine (3-Lactone with Penicillamine Derivatives... 

The second synthesis approach, carried out by Shanzer and Libman, employed L-serine (3-lactones 91, derived from N-trityl L-serine (92) in 26% yield (Fig. 16a). 

The anionic polymerization of A(-benzyloxycarbonyl-L-serine 3-lactone leads to poly(A -acyl-L-serine ester) My, = ca. 40 000), from which poly(L-serine ester hydrochloride) can be obtained by hydrogenation. ... 

In summary, ring opening of serine-3-lactones is an attractive method for generating optically pure 3-substituted alanines the synthesis usually occurs with little or no epimerization. 

Although the most frequently used nomenclature for AHLs was initially based on a 3-5 letter codes based on names e.g. BHL for N-butyryl-L-homo-serine lactone, OHHL for AT-(3-oxohexanoyl)-L-homoserine lactone or OdDHL for N-(3-oxododecanoyl)-L-homoserine lactone, the rapid expansion in the range of AHL molecules discovered has led to changes in this nomenclature. Currently, the accepted abbreviations are a structure-based short-hand notations e.g. C4-HSL for N-butyryl-L-homoserine lactone, 3-oxo-C6-HSL (or 30,C6-HSL) for AT-(3-oxohexanoyl)-L-homoserine lactone or 3-hydroxy-C12-HSL (or 30H,C12-HSL) for N-(3-hydroxydodecanoyl)-L-homoserine lactone. 

A completely different approach to the total synthesis of enterobaetin has been reported by Shanzer and Libman 100>. This is based on a single-step conversion of the tritylated serine-lactone to the cyclic triester enterobaetin backbone via the use of a cyclic organotin compound as template. This is followed by subsequent replacement of the trityl protecting groups by catechol residues to yield enterobaetin. 

N-tert-Butoxycarbonyl-L-serine lactone Carbamic acid, (2-oxo-3-oxetanyl)-,... 

SYNTHESIS OF N-tert-BUTOXY-CARBONYL-L-SERINE LACTONE AND THE p-TOLUENESULFONIC ACID SALTOF (S)-3-AMINO-... 

V-(Trimethylsilyl)imidazole has proven to be a good nucleophile for the ring opening of epoxides,but a moderate one for the ring opening of either optically pure iV-Cbz-L-serine- -lactone or thiiranium ion intermediates. ... 

Sirolimus (SRL), also termed rapamycin is a macrolide lactone isolated from the ascomycete species Stre-ptomyces hygroscopicus. After binding to its cytosolic receptor FKBP-12 the resulting complex inhibits the multifunctional serine-threonine kinase mTOR (mammalian target of rapamycin). Inhibition of mTOR prevents activation of the p70S6 kinase and successive... 

Lipases have also been used as initiators for the polymerization of lactones such as /3-bu tyro lac tone, <5-valerolactone, e-caprolactone, and macrolides.341,352-357 In this case, the key step is the reaction of lactone with die serine residue at the catalytically active site to form an acyl-enzyme hydroxy-terminated activated intermediate. This intermediate then reacts with the terminal hydroxyl group of a n-mer chain to produce an (n + i)-mer.325,355,358,359 Enzymatic lactone polymerization follows a conventional Michaelis-Menten enzymatic kinetics353 and presents a controlled character, without termination and chain transfer,355 although more or less controlled factors, such as water content of the enzyme, may affect polymerization rate and the nature of endgroups.360... 

C 3H,5N04 1148-11-4) see Angiotensinamide Captopril 7V-benzyloxycarbonyl-L-proline tert-butyl ester (C17H23NO4 16881-39-3) see Captopril 7V-benzyloxycarbonyl-L-serine (CiiHijNOj 7745-80-8) see Nelfinavir mesylate iV-benzyloxycarbonyl-L-serine-P-lactone (C Hi,N04 26054-60-4) see Nelfinavir mesylate 7V-benzyloxycarbonylsuccinimide... 

Separation methods, multichromato-graphic la 56 Serine la 246,356 lb 132 Serotonin la 70,76,239,240,262,355, 380 lb 37-39,231,243,348 Serotonin metabolites lb 327 Serum lipids la 89 Serum proteins la 74 Sesquiterpene derivatives lb 239,446 Sesquiterpene esters lb 239 Sesquiterpene glucosides la 327 Sesquiterpene lactones lb 448 Sevin lb 387-389 Si 50 000, specific surface area la 91 Silica gel, caffeine-impregnated la 85 -, surface modified la 3 Silica gel 60, specific surface area la 91... 

FIGURE 2 Polymers that can be derived firom L-serine. (a) Poly-(serine ester) was obtained by ring opening polymerization of N-protected serine-p-lactones (19). (b) Poly(serine imine) has appar-... 

Bromomethyl-3,4-dibromo-3,4-dihydrocoumarin 1 (Fig. 11.4) and its chloro-methylated analogue 2b rapidly and progressively inactivate a-chymotrypsin and also the activities of a series of trypsin-like proteases. A benzyl substituent characteristic of good substrates of a-chymotrypsin was introduced at the 3-position to make inhibition more selective. This substituted dihydrocoumarin 3 irreversibly inhibited a-chymotrypsin and other proteases. These functionalized six-membered aromatic lactones, and their five- and seven-membered counterparts, 3//-benzofuran-2-ones 2a26 and 4,5-dihydro-3//-benzo[b]oxepin-2-ones 2c,27 were the first efficient suicide inhibitors of serine proteases. Their postulated mechanism of action is shown in Scheme 11.2. 

After the nucleophilic attack by the hydroxyl function of the active serine on the carbonyl group of the lactone, the formation of the acyl-enzyme unmasks a reactive hydroxybenzyl derivative and then the corresponding QM. The cyclic structure of the inhibitor prevents the QM from rapidly diffusing out of the active center. Substitution of a second nucleophile leads to an irreversible inhibition. The second nucleophile was shown to be a histidine residue in a-chymotrypsin28 and in urokinase.39 Thus, the action of a functionalized dihydrocoumarin results in the cross-linking of two of the most important residues of the protease catalytic triad. 

However, there are two problems with these unconjugated lactones lack of selectivity and limited stability of the inhibitor in biological buffers. Coumarin carboxylates have been developed to improve selectivity toward a given serine protease (Section 11.4.1). On the other hand, the amide bond is chemically and enzymatically much more stable than the ester one. This raised the question of whether a starting functionalized lactam behaved like the previous lactones and generated in situ a quinonimine methide, the aza-analogue of the quinone methide (Section 11.5). 

Amino acid synthesis.1 Optically pure amino acids can be prepared in two steps from serine, readily available as either the d- or L-enantiomer. Reaction of N-benzylserine (or of N-benzyl-N-Boc-serine) with the preformed Mitsunobu reagent in CH3CN at -55° provides the protected serine (J-lactone (2) in almost quantitative yield. The lactone reacts with lithium organocuprates (R2CuLi) to... 

The hydroxymethyl and carboxyl group of Ser can participate in pyrazole-ring formation, as shown in the transformation of A -protected L-Ser with the Mitsunobu reagent into a /3-lactone which afforded the N-protected serine hydrazide upon treatment with methyl hydrazine. Cyclization to 25 was achieved by diisopropyl azodicarboxylate (DIAD) and TPP [90H(31)79]. 

Pilocarpine (30) is one of a series of related alkaloids found in the South American plant genus Pilocarpus, known commonly as Jaborandi leaf, which was used in traditional medicine to induce sweating and urination. The molecular structure of (30) bears similarities to ACh (2) since the positively-charged N-atom and the lactone binding to the serine are about the same distance apart. Chewing the leaf results in typical features... 

Synthesis of N-Protected a-Amino Acids from N-(Benzyloxycarbonyl)-L-Serine via Its g-Lactone N -(Benzyloxycarbonyl)-p-(Pyrazol-1-yl)-L-Alanine... 

The mechanism of the enzymatic polymerization is shown in Fig. 25 and can be decomposed into three main steps. First, a complex is formed between the enzyme and the lactone. The second step is based on the nucleophihc activation of the lactone by the hydroxyl function belonging to a serine residue of the active... 

In contrast to the syntheses described above, which all start from cystine derivatives to form lanthionine, the lanthionine syntheses in this section all start from a protected cysteine as the nucleophilic precursor, which is then allowed to react with any of a variety of different substrates. These subsequent reactions are the Michael addition with dehydroalanine, the nucleophilic substitution of halo amino acids, or the ring-opening reaction of serine p-lactones and aziridines, respectively. However, it must be emphasized that the Michael... 

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