Chemoenzymatic Synthesis of 4-Amino-2-hydroxy Acids: A Comparison of Mutant and Wild-Type Oxidoreductases
摘要:
We describe a new chemoenzymatic synthesis of enantiopure 4-amino-2-hydroxy acids using two biotransformations in a single-pot process in aqueous medium. These compounds are valuable as gamma-turn mimics for investigations into the secondary structure of peptides. The enzyme substrates are a series of carbobenzyloxy (CBZ)-protected 4-amino-2-keto esters, prepared efficiently from the L-amino acids, alanine, leucine, phenylalanine, and valine. First, the alpha-amino acids were converted to the corresponding beta-amino acids in a simple five-step procedure. A further one-carbon homologation via ozonolysis of the corresponding beta-keto cyanophosphoranes gave the required alpha-keto esters in good yield. The enzyme catalyzed hydrolyses of all the alpha-keto esters to the corresponding alpha-keto acids proceeded smoothly with the lipase from Candida rugosa. Using the same reaction pot, it was found that wild-type lactate dehydrogenases from either Bacillus stearothermophilus (BS-LDH) or Staphylococcus epidermidis (SE-LDH) could be used to specifically reduce the ketone of the alanine-derived alpha-keto acid 2, giving the (S)- and (R)-2-hydroxy acids, respectively, in good yields. However, the more bulky alpha-keto acids 3, 4, and 5 (derived from valine, leucine, and phenylalanine) were not substrates for these enzymes. In contrast, the genetically engineered H205Q mutant of D-hydroxyisocaproate dehydrogenase proved to be an ideal catalyst for the reduction of all the alpha-keto acids 2-5, giving excellent yields of the CBZ-protected (2R,4S)-4-amino-2-hydroxy acids as single diastereomers. This genetically engineered oxidoreductase has great potential value in synthesis due to its broad substrate specificity and high catalytic activity. For example, reduction of 1 mmol of N-protected (S)-4-amino-2-oxopentanoic acid 2 took just 4 h with the H205Q mutant giving, after esterification, the (R)-2-alcohol 25 in 85% yield, whereas with SE-LDH the reaction required 4 days to give a 67% yield of 25.
Potent and systemically active aminopeptidase N inhibitors designed from active-site investigation
摘要:
Derivatives of amino acids bearing various zinc-coordinating moieties (SH, COOH, CONHOH, and PO3H2) were synthesized and tested for their ability to inhibit aminopeptidase N (APN). Among them, beta-amino thiols were found to be the most efficient with IC50's in the 11-50 nM range. These results suggest that the S1 subsite of APN is a deep but not very large hydrophobic pocket, optimally fitting side chains of moderate bulk endowed with some degree of freedom. The iv administration of the inhibitors, alone, did not induce antinociceptive responses on the hot plate test in mice. However, in presence of 10 mg/kg acetorphan, a prodrug of the neutral endopeptidase inhibitor thiorphan, these compounds gave a large increase in the jump latency time with ED50's of 2 and 2.4 mg/kg for the disulfides of methioninethiol [H2NCH(CH2CH2SCH3)CH2S]2 and S-oxomethioninethiol [H2NCH(CH2CH2S(O)CH3)CH2S]2, respectively. These results show that the disulfide forms of beta-amino thiols are efficient prodrugs of aminopeptidase N inhibitors capable of crossing the blood-brain barrier.
To discover broad spectrum antifungal agents, two strategies were applied, and a novel class of l-amino alcohol derivatives were designed and synthesized. 3-F substituted compounds 14i, 14n, 14s and 14v exhibited excellent antifungal activities with broad antifungal spectra against C. albicans and C. tropicalis, with MIC values in the range of 0.03–0.06 μg/mL, and against A. fumigatus and C. neoformans
Dialkyl amides of L-valine, L-isoleucine, and L-tert-leucine (2) are excellent chiral auxiliaries for the construction of quaternary stereocenters at ambient temperature. Enaminoesters 3, prepared from these auxiliaries 2 and Michael donors 1, undergo a copper-catalyzed asymmetricMichaelreaction with methyl vinyl ketone (MVK, 4) to afford products 5 in 70-90% yield and 90-99% ee (enantiomeric excess)
Whereas palladium-catalyzed reaction of N-arylsulfonyl-alpha-amino allenes with an aryl iodide (4 equiv) in the presence of potassium carbonate (4 equiv) in DMF at around 70 degrees C affords the corresponding 3-pyrroline derivatives, the reaction in refluxing 1,4-dioxane under otherwise identical conditions yields exclusively or most predominantly the corresponding 2-alkenylaziridines bearing an aryl
A rapid entry to amino acid derived diverse 3,4-dihydropyrazines and dihydro[1,2,3]triazolo[1,5-a]pyrazines through 1,3-dipolar cycloaddition
作者:Saurav Bera、Gautam Panda
DOI:10.1039/c4ob00639a
日期:——
synthesis of diverse 3,4-dihydropyrazines, 6,7-dihydro-[1,2,3]triazolopyrazines and 7,8-dihydro-[1,2,3]triazolodiazepines through intramolecular 1,3-dipolar cycloaddition fromaminoacid derived common intermediates with high yields is described. Moreover, one-pot access to optically active 3-aryl substituted 6,7-dihydro-[1,2,3]triazolo[1,5-a]pyrazines in the palladium–copper co-catalytic system has
通过分子内1,3-高效,通用和实用地合成各种3,4-二氢吡嗪,6,7-二氢-[1,2,3]三唑并吡嗪和7,8-二氢-[1,2,3]三唑并二氮杂pine描述了从氨基酸衍生的常见中间体以高收率进行偶极环加成。此外,在此方法中,还可以通过一锅获得光学活性的3-芳基取代的6,7-二氢-[1,2,3]三唑并[1,5- a ]吡嗪在钯-铜共催化体系中的应用。工作。容易获得的基材和操作简便性使该工艺适合于进一步探索。
Synthesis of Enkephalin Analog with Leucinthiol at<i>C</i>-Terminus as Probe for Thiol Group in Opiate Receptors
Enkephalin analog with thiol group at C-terminus, [D-Ala2, Leu(CH2SH)5]enkephalin, was synthesized as possible probe for the essential thiol group in opiate receptors. In order to protect the free SH group of leucinthiol, oxidized Boc-L-leucinthiol dimer was prepared from L-leucinol (2-amino-4-methyl-1-pentanol) to elongate the enkephalin sequence. SH-Containing monomeric enkephalin analog was obtained
在 C 端具有硫醇基团的脑啡肽类似物 [D-Ala2, Leu(CH2SH)5] 脑啡肽被合成为阿片受体中必需硫醇基团的可能探针。为了保护亮氨酸硫醇的游离 SH 基团,从 L-亮氨酸(2-氨基-4-甲基-1-戊醇)制备氧化的 Boc-L-亮氨酸硫醇二聚体以延长脑啡肽序列。含 SH 的单体脑啡肽类似物是通过在 50% AcOH 中用锌处理从二聚体中获得的,它对 mu 阿片受体具有高亲和力。