Enantioselective synthesis of L-phosphinothricin from L-methionine and L-glutamic acid via L-vinylglycine

Biomanufacture of L-homoserine lactone building block: A strategy for preparing γ-substituted L-amino acids by modular reaction

A strain high-performance of esterase producing bacteria was screened from soil, which could selectively hydrolyze D-homoserine lactone from its racemate to achieve the resolution of L- homoserine lactone with more than 99% e.e. in 48% yield. L-homoserine lactone building block was then converted to L-α-amino-γ-bromobutyronic acid chiral blocks, which reacted with various nucleophilic reagent modules could to be applied to prepare L-γ- substituted α-amino acids such as L-selenomethionine, L-methionine, L-glufosinate and L-selenocystine. Its advantages included high selectivity of biocatalytic resolution reactions, high optical purity of products, racemic recycle of D-substrates and modular reaction, which simplified the production process of these products and highlighted the power of biological manufacturing.

Heterologous expression of a deacetylase and its application in L-glufosinate preparation

With potent herbicidal activity, biocatalysis synthesis of L-glufosinate has drawn attention. In present research, NAP-Das2.3, a deacetylase capable of stereoselectively resolving N-acetyl-L-glufosinate to L-glufosinate mined from Arenimonas malthae, was heterologously expressed and characterized. In Escherichia coli, NAP-Das2.3 activity only reached 0.25 U/L due to the formation of inclusive bodies. Efficient soluble expression of NAP-Das2.3 was achieved in Pichia pastoris. In shake flask and 5 L bioreactor fermentation, NAP-Das2.3 activity by recombinant P. pastoris reached 107.39 U/L and 1287.52 U/L, respectively. The optimum temperature and pH for N-acetyl-glufosinate hydrolysis by NAP-Das2.3 were 45 °C and pH 8.0, respectively. The Km and Vmax of NAP-Das2.3 towards N-acetyl-glufosinate were 25.32 mM and 19.23 μmol mg-1 min-1, respectively. Within 90 min, 92.71% of L-enantiomer in 100 mM racemic N-acetyl-glufosinate was converted by NAP-Das2.3. L-glufosinate with high optical purity (e.e.P above 99.9%) was obtained. Therefore, the recombinant NAP-Das2.3 might be an alternative for L-glufosinate biosynthesis.

Phosphorus-containing amino acids with a P–C bond in the side chain or a P–O, P–S or P–N bond: from synthesis to applications

Strategies for the preparation of phosphorus-containing amino acids and their utility in the organic chemistry, physico-chemistry, agrochemistry, and pharmacology fields are reported.

Enantioselective Degradation and Chiral Stability of Glufosinate in Soil and Water Samples and Formation of 3-Methylphosphinicopropionic Acid and N-Acetyl-glufosinate Metabolites

Two enantiomers of glufosinate were separated under reverse-phase conditions on a chiral crown stationary phase (CROWNPAK CR(+)). An efficient and reliable chiral analytical method was developed to determine the glufosinate enantiomers and two metabolites in soil and water samples using high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS). The linearities of the matrix-matched calibration curves in five water and four soil samples were good with a correlation coefficient R² > 0.998, and the mean recoveries were 85.2-100.4%, with relative standard deviations of 1.0-7.1%. l-Glufosinate was degraded faster than d-glufosinate in four nonsterile natural soil and two nonsterile natural water samples. The degradation half-lives of the enantiomers ranged from 3.4 to 33.0 days in the soil samples, but glufosinate was stable in the five water samples, less than 22% of the applied substance degraded at the end of the experiment (100 days). Degradation in sterile soil was not enantioselective. The two enantiomers were configurationally stable in the four soil and five water samples. In most cases of glufosinate degradation in soils, the percentage of 3-methylphosphinicopropionic in relation to the parent was higher than that of N-acetyl-glufosinate. l-Glufosinate was preferentially degraded in the four soils, and formation of 3-methylphosphinicopropionic acid and N-acetyl-glufosinate was enantiomer dependent.

Recent Developments in the Addition of Phosphinylidene-Containing Compounds to Unactivated Unsaturated Hydrocarbons: Phosphorus-Carbon Bond-Formation via Hydrophosphinylation and Related Processes

The reactions of phosphinylidene-containing compounds with unactivated unsaturated hydrocarbons are reviewed. The review is organized by phosphorus-containing functional group types. Free-radical and metal-catalyzed additions of R(1)R(2)P(O)H to alkenes, alkynes, and related compounds, deliver functionalized organophosphorus compounds RP(O)R(1)R(2), including H-phosphinates, phosphinates, tertiary phosphine oxides, and phosphonates. The review covers the literature up to February 2008.

Allylic phosphinates via palladium-catalyzed allylation of H-phosphinic acids with allylic alcohols

A novel catalytic allylation of H-phosphinic acids is described. Using Pd/xantphos (2 mol %), H-phosphinic acids react directly with allylic alcohols to produce P-allylated disubstituted phosphinic acids.

α-Vinylic Amino Acids: Occurrence, Asymmetric Synthesis and Biochemical Mechanisms

This report presents an overview of the family of naturally occurring 'vinylic' amino acids, namely those that feature a C-C double bond directly attached to the α-carbon, along the side chain. Strategies that have been brought to bear on the stereocontrolled synthesis of these olefinic amino acids are surveyed. The mechanistic diversity by which such 'vinylic triggers' can be actuated in a PLP (pyridoxal phosphate) enzyme active site is then highlighted by discussions of vinylglycine (VG), its substituted congeners, particularly AVG [4E-(2'-aminoethoxy)vinylglycine], and a naturally occurring VG-progenitor, SMM (S-methylmethionine).

Phosphinic acid pseudopeptides analogous to glutamyl-gamma-glutamate: synthesis and coupling to pteroyl azides leads to potent inhibitors of folylpoly-gamma-glutamate synthetase

Several routes to a complex phosphinate phosphapeptide analogous to the gamma-glutamyl peptide Glu-gamma-Glu have been investigated. Formation of gamma-phosphono glutamate derivatives via addition of a phosphorus-based radical to protected vinylglycine was found to be of limited value because of the elevated temperatures required. Alkylation and conjugate addition reactions of trivalent phosphorus (P(III)) species were investigated. In situ generation of bis-trimethylsilyl esters of phosphinous acids proved to be an effective route to phosphinates of modest structural complexity. However, this chemistry could not be extended to the incorporation of an amino acid moiety at the N-terminal side of the desired phosphinate. A successful synthesis of the target phosphinate phosphapeptide was effected using P(III) chemistry and dehydrohalogenation to yield an alpha,beta-unsaturated phosphinic acid ester, following which conjugate addition of diethylacetamido malonate and acid-mediated hydrolysis afforded the desired phosphinate phosphapeptide. Coupling of the unprotected phosphinate phosphapeptide with two acyl azides derived from folic acid and methotrexate led to the corresponding pteroylphosphapeptides of interest as possible mimics of tetrahedral intermediates in the reaction catalyzed by folylpolyglutamate synthetase.

Glufosinate (phosphinothricin), a natural amino acid with unexpected herbicidal properties

Glufosinate ammonium (phosphinothricin ammonium) (GLA) is the active ingredient of Basta and several other herbicides used worldwide. It is produced as part of the tripeptide L-phosphinothricyl-L-alanyl-L-alanin, which was first isolated from Streptomyces viridichromogenes or Streptomyces hygroscopicus. Its structure is confirmed by degradation and synthesis. Several processes for the preparation of D,L- and L-phosphinothricin are described. Glufosinate is a structural analog of glutamate and inhibits the glutamine synthetase. The result is a rapid build-up of a high ammonia level and a concomitant depletion of glutamine and several other amino acids in the plant. These effects are accompanied by a rapid decline of photosynthetic CO2-fixation and are followed by chlorosis and desiccation. The results of numerous toxicological studies show that glufosinate ammonium and its commercial formulations are safe for users and consumers under the conditions of recommended use. The fast and complete degradation in soil and surface water prevents movement of residues into groundwater. The toxicological threshold levels for all the nontarget organisms tested are well above the potential exposure levels and therefore do not reflect any hazard for nontarget organisms in the ecosystem. Basta is a nonselective foliar applied herbicide for the control of undesirable mono- and dicotyledonous plants in orchards, vineyards, and plantations for minimum tillage, and as a harvest aid. A synthetic phosphinothricin acetyltransferase (PAT) gene has been introduced via Agrobacterium tumefaciens into dicot crops, such as like tobacco, tomato, spring and winter rapeseed, alfalfa, and several horticultural crops. The PAT gene was also successfully introduced into maize protoplasts that could be regenerated into fertile plants. All transgenic crop plants tolerated a two- to threefold field dosage of Basta.