Aspartic acid derivatives with branched N-alkyl or N-arylalkyl substituents are valuable precursors to artificial dipeptide sweeteners such as neotame and advantame. The development of a biocatalyst to synthesize these compounds in a single asymmetric step is an as yet unmet challenge. Reported here is an enantioselective biocatalytic synthesis of various difficult N-substituted aspartic acids, including N-(3,3-dimethylbutyl)-l -aspartic acid and N-[3-(3-hydroxy-4-methoxyphenyl)propyl]-l -aspartic acid, precursors to neotame and advantame, respectively, using an engineered variant of ethylenediamine-N,N′-disuccinic acid (EDDS) lyase from Chelativorans sp. BNC1. This engineered C–N lyase (mutant D290M/Y320M) displayed a remarkable 1140-fold increase in activity for the selective hydroamination of fumarate compared to that of the wild-type enzyme. These results present new opportunities to develop practical multienzymatic processes for the more sustainable and step-economic synthesis of an important class of food additives. 相似文献
The title bis(glycyl‐l ‐aspartic acid) oxalate complex {systematic name: bis[2‐(2‐ammonioacetamido)butanedioic acid] oxalate 0.4‐hydrate}, 2C6H11N2O5+·C2O42−·4H2O, crystallizes in a triclinic space group with the planar peptide unit in a trans conformation. The asymmetric unit consists of two glycyl‐l ‐aspartic acid molecules with positively charged amino groups and neutral carboxyl groups, and an oxalate dianion. The twist around the C—Cα bond indicates that both the peptide molecules adopt extended conformations, while the twist around the N—Cα bond shows that one has a folded and the other a semi‐extended state. The present complex can be described as an inclusion compound with the dipeptide molecule as the host and the oxalate anion as the guest. The usual head‐to‐tail sequence of aggregation is not observed in this complex, as is also the case with the glycyl‐l ‐aspartic acid dihydrate molecule. The study of aggregation and interaction patterns in binary systems is the first step towards understanding more complex phenomena. This further leads to results that are of general interest in bimolecular aggregation. 相似文献
The first synthesis of a natural N‐glycosylated 3‐acyltetramic acid is reported. Aurantoside G ( 1 g ), a deep‐red metabolite of the marine sponge Theonella swinhoei, is highly delicate in the pure state. It features a chlorinated dodecapentaenoyl side chain at an l ‐asparagine‐derived tetramic acid, the ring nitrogen atom of which is linked to a β‐configured d ‐xylose. The side chain was built through consecutive Wittig and HWE reactions and used to N‐acylate the amino group of an asparaginate that had already been N‐xylosylated through a Fukuyama–Mitsunobu reaction. This N‐acylation step fixes the β‐configuration of the xylose, which is essential for the antifungal activity, but only if the sugar carries bulky, electron‐rich protecting groups such as PMB. In the final step, the heterocycle was closed quantitatively through a basic Lacey–Dieckmann condensation of an entirely unprotected precursor. 相似文献
We have developed and validated a high‐performance liquid chromatography method that uses monolithic silica disk‐packed spin columns and a monolithic silica column for the simultaneous determination of NG‐monomethyl‐l ‐arginine, NG,NG‐dimethyl‐l ‐arginine, and NG,NG′‐dimethyl‐l ‐arginine in human plasma. For solid‐phase extraction, our method employs a centrifugal spin column packed with monolithic silica bonded to propyl benzenesulfonic acid as a cation exchanger. After pretreatment, the methylated arginines are converted to fluorescent derivatives with 4‐fluoro‐7‐nitro‐2,1,3‐benzoxadiazole, and then the derivatives are separated on a monolithic silica column. l ‐Arginine concentration was also determined in diluted samples. Standard calibration curves revealed that the assay was linear in the concentration range 0.2–1.0 μM for methylated arginines and 40–200 μM for l ‐arginine. Linear regression of the calibration curve yielded equations with correlation coefficients of 0.999 (r2). The sensitivity was satisfactory, with a limit of detection ranging from 3.75 to 9.0 fmol for all four compounds. The RSDs were 4.3–4.8% (intraday) and 3.0–6.8% (interday). When this method was applied to samples from six healthy donors, the detected concentrations of NG‐monomethyl‐l ‐arginine, NG,NG‐dimethyl‐l ‐arginine, NG,NG′‐dimethyl‐l ‐arginine and l ‐arginine were 0.05 ± 0.01, 0.41 ± 0.07, 0.59 ± 0.11, and 83.8 ± 30.43 μM (n = 6), respectively. 相似文献
Enantioselective resolution is realized by combining potentiometry with ligand exchange (CE) in a new method called chiral ligand exchange potentiometry (CLEP). A chiral selector, N‐carbobenzoxy‐L ‐aspartic acid (N‐CBZ‐L‐Asp), preferentially recognizes D ‐aspartic acid (D‐Asp) and undergoes ligand exchange with the enantiomeric labile coordination complexes of [Cu(II)(D‐Asp)2] or [Cu(II)(L‐Asp)2] to form a diastereoisomeric complex [(D‐Asp)Cu(II)(N‐CBZ‐L‐Asp)] (a) or [(L‐Asp)Cu(II)(N‐CBZ‐L‐Asp)] (b). Considerable stereoselectivity occurs in the formation of these diastereoisomeric complexes, and their net charges were ?2 (a) and 0 (b), respectively, resulting in different Nernst factor (electrode slope), thus enabling chiral D‐Asp to be distinguished by potentiometry without any pre‐ or postseparation processes. 相似文献
The crystal structure of the lipoundecapeptide amphisin, presented here as the tetrahydrate, C66H114N12O20·4H2O, originating from non‐ribosomal biosynthesis by Pseudomonas sp. strain DSS73, has been solved to a resolution of 0.65 Å. The primary structure of amphisin is β‐hydroxydecanoyl‐d ‐Leu‐d ‐Asp‐d ‐allo‐Thr‐d ‐Leu‐d ‐Leu‐d ‐Ser‐l ‐Leu‐d ‐Gln‐l ‐Leu‐l ‐Ile‐l ‐Asp (Leu is leucine, Asp is aspartic acid, Thr is threonine, Ser is serine, Gln is glutamine and Ile is isoleucine). The peptide is a lactone, linking Thr4 Oγ to the C‐terminal. The stereochemistry of the β‐hydroxy acid is R. The peptide is a close analogue of the cyclic lipopeptides tensin and pholipeptin produced by Pseudomonas fluorescens. The structure of amphisin is mainly helical (310‐helix), with the cyclic peptide wrapping around a hydrogen‐bonded water molecule. This lipopeptide is amphiphilic and has biosurfactant and antifungal properties. 相似文献
The racemization of d ‐aspartic acid to l ‐aspartic acid has been successfully performed with a coupled enzyme system at 90 °C and a pH of about 4.0 by the assay of high‐performance liquid chromatography. This coupled enzymatic racemization is a successive two‐step reaction first induced by d ‐amino acid oxidase and a subsequent coupled reaction by an aminotransferase clonezyme with the help of coenzyme pyridoxal 5′‐phosphate and cosubstrate l ‐glutamate. Due to the very high temperature, part of the l ‐aspartic acid is produced by the thermal effect. In fact the thermal racemization for aspartic acid can proceed from either d ‐ or l ‐aspartic acid via an intermediate fumaric acid and leads to the formation of d ,l ‐malic acid. The formation of α‐oxalacetic acid formed irreversibly from d ‐aspartic acid with d ‐amino acid oxidase can induce a side reaction to l ‐alanine. The thermal effect may also be responsible for the production of d ‐, and l ‐alanine. 相似文献
O‐(2‐Acetamido‐3,4,6‐tri‐O‐acetyl‐D ‐glucopyranosylidene)amino N‐phenylcarbamate ( 1 ), an established inhibitor of β‐N‐acetylglucosaminidases, has been prepared by an improved six‐step synthesis from N‐acetyl‐D ‐glucosamine. 相似文献
The formation of a N?N bond is a unique biochemical transformation, and nature employs diverse biosynthetic strategies to activate nitrogen for bond formation. Among molecules that contain a N?N bond, biosynthetic routes to diazeniumdiolates remain enigmatic. We here report the biosynthetic pathway for the diazeniumdiolate‐containing amino acid l ‐alanosine. Our work reveals that the two nitrogen atoms in the diazeniumdiolate of l ‐alanosine arise from glutamic acid and aspartic acid, and we clarify the early steps of the biosynthetic pathway by using both in vitro and in vivo approaches. Our work demonstrates a peptidyl‐carrier‐protein‐based mechanism for activation of the precursor l ‐diaminopropionate, and we also show that nitric oxide can participate in non‐enzymatic diazeniumdiolate formation. Furthermore, we demonstrate that the gene alnA, which encodes a fusion protein with an N‐terminal cupin domain and a C‐terminal AraC‐like DNA‐binding domain, is required for alanosine biosynthesis. 相似文献
The synthesis of triblock copolymers based on polysarcosine, poly‐N‐ε‐t‐butyloxycarbonyl‐l ‐lysine, and poly‐N‐ε‐t‐trifluoroacetyl‐l ‐lysine by ring‐opening polymerization of the corresponding α‐amino acid N‐carboxyanhydrides (NCAs) is described. For the synthesis of N‐ε‐t‐butyloxycarbonyl‐l ‐lysine (lysine(Boc)) NCAs, an acid‐free method using trimethylsilylchloride/triethylamine as hydrochloric acid (HCl) scavengers is presented. This approach enables the synthesis of lysine(Boc) NCA of high purity (melting point 138.3 °C) in high yields. For triblock copolypept(o)ides, the degree of polymerization (Xn) of the polysarcosine block is varied between 200 and 600; poly‐N‐ε‐t‐butyloxycarbonyl‐l ‐lysine and poly‐N‐ε‐t‐trifluoroacetyl‐l ‐lysine blocks are designed to have a Xn in the range of 10–50. The polypeptide‐polypeptoid hybrids (polypept(o)ides) can be synthesized with precise control of molecular weight, high end group integrity, and dispersities indices between 1.1 and 1.2. But more important, the use of tert‐butyloxycarbonyl‐ and trifluoroacetyl‐protecting groups allows the selective, orthogonal deprotection of both blocks, which enables further postpolymerization modification reactions in a block‐selective manner. Therefore, the presented synthetic approach provides a versatile pathway to triblock copolypept(o)ides, in which functionalities can be separated in specific blocks.
Two amino acids play a key role in the first total synthesis of lycopalhine A. l ‐glutamic acid serves as a convenient chiral starting material for the 13‐step synthesis, and l ‐proline promotes an unusual 5‐endo‐trig Mannich cyclization that generates the central pyrrolidine ring of the Lycopodium alkaloid. The bicyclo[3.3.0]octanol moiety of the molecule is formed through an intramolecular aldol addition that may occur spontaneously in nature. 相似文献
The crystal structure of N‐(l ‐2‐aminobutyryl)‐l ‐alanine, C7H14N2O3, is closely related to the structure of l ‐alanyl‐l ‐alanine, both being tetragonal, while the retro‐analogue 2‐(l ‐alanylamino)‐l ‐butyric acid 0.33‐hydrate, C7H14N2O3·0.33H2O, forms a new type of molecular columnar structure with three peptide molecules in the asymmetric unit. 相似文献
Disulfiram has been used as a deterrent in the treatment of alcohol abuse for almost 60 years. Our laboratory has shown that a disulfiram metabolite, S‐(N,N‐diethylcarbamoyl) glutathione (carbamathione), is formed from disulfiram and appears in the brain after the administration of disulfiram. Carbamathione does not inhibit aldehyde dehydrogenase but has been shown to be a partial non‐competitive inhibitor of the N‐methyl‐D ‐aspartic acid glutamate (Glu) receptor. In light of disulfiram's apparent clinical effectiveness in cocaine dependence, and carbamathione's effect on the N‐methyl‐D ‐aspartic acid receptor, the effect of carbamathione on brain Glu and γ‐aminobutyric acid (GABA) needs to be further examined. A CE‐LIF method based on derivatization with napthalene‐2,3‐dicarboxyaldehyde to simultaneously detect both neurotransmitter amino acids and carbamathione in brain microdialysis samples is described. The separation of Glu, GABA and carbamathione was carried out using a 50 mmol/L boric acid buffer (pH 9.6) on a 75 cm×50 μm id fused‐silica capillary (60 cm effective) at +27.5 kV voltage with a run time of 11 min. The detection limits for Glu, GABA and carbamathione were 6, 10 and 15 nmol/L, respectively. This method was used to monitor carbamathione and the amino acid neurotransmitters in brain microdialysis samples from the nucleus accumbens after the administration of an intravenous dose of the drug (200 mg/kg) and revealed a carbamathione‐induced change in GABA and Glu levels. This method demonstrates a simple, rapid and accurate measurement of two amino acid neurotransmitters and carbamathione for in vivo monitoring in the brain using microdialysis sampling. 相似文献
The novel natural product xyloallenoide A, isolated from the marine mangrove endophytic fungus from the South China Sea, and its diastereoisomer xyloallenoide A1, which contain N‐methyl‐substituted amino acids, were synthesized. The absolute configurations of the amino acid units of xyloallenoide A were finally confirmed to be L ‐Lys, Me‐D ‐Val, and Me‐L ‐Ala. This report represents a practical and attractive alternative for the synthesis of N‐methyl‐substituted cyclotripeptides. In the preliminary bioassay, synthetic xyloallenoide A showed marginal activities against KB (IC50=9.6 μM ) and KBv200 cells (IC50=10.3 μM ), and xyloallenoide A1 was inactive against KB and KBv200 cells. 相似文献