Jesús M. Peregrina

Investigations of La Rioja terroir for wine production using 1H NMR metabolomics.

In this study, La Rioja wine terroir was investigated by the use of (1)H NMR metabolomics on must and wine samples. Rioja is a small wine region in central northern Spain which can geographically be divided into three subareas (Rioja Alta, Rioja Baja, and Rioja Alavesa). The winemaking process from must, through alcoholic and malolactic fermentation, was followed by NMR metabolomics and chemometrics of nine wineries in the Rioja subareas (terroirs). Application of interval extended canonical variate analysis (iECVA) showed discriminative power between wineries which are geographically very close. Isopentanol and isobutanol compounds were found to be key biomarkers for this differentiation.

A thorough study on the use of quantitative 1H NMR in Rioja red wine fermentation processes.

In this study, we focused our attention on monitoring the levels of important metabolites of wine during the alcoholic and malolactic fermentation processes by quantitative nuclear magnetic resonance (qNMR). Therefore, using (1)H NMR, the method allows the simultaneous quantification of ethanol, acetic, malic, lactic, and succinic acids, and the amino acids proline and alanine, besides the ratio proline/arginine through fermentation of must of grapes corresponding to the Tempranillo variety. Each (1)H NMR spectrum gives direct and visual information concerning these metabolites, and the effectiveness of each process was assessed and compared by carrying out analyses using infrared spectroscopy to ethanol and acetic acid. The quantitative data were explained with the aid of chemometric algorithms.

Enantioselective synthesis of (S)- and (R)-α-methylserines: application to the synthesis of (S)- and (R)-N-Boc-N,O-isopropylidene-α-methylserinals

Abstract This report describes the synthesis of enantiomerically pure ( S )- and ( R )-α-methylserines on a multigram scale, starting from the Weinreb amide of 2-methyl-2-propenoic acid and using a stereodivergent synthetic route that involves a Sharpless asymmetric dihydroxylation reaction. As a synthetic application of these quaternary α-amino acids, they were used as starting materials in the synthesis of the well-known valuable homochiral ( S )- and ( R )- N -Boc- N , O -isopropylidene-α-methylserinal building blocks.

Substrate-guided front-face reaction revealed by combined structural snapshots and metadynamics for the polypeptide N-acetylgalactosaminyltransferase 2.

The retaining glycosyltransferase GalNAc-T2 is a member of a large family of human polypeptide GalNAc-transferases that is responsible for the post-translational modification of many cell-surface proteins. By the use of combined structural and computational approaches, we provide the first set of structural snapshots of the enzyme during the catalytic cycle and combine these with quantum-mechanics/molecular-mechanics (QM/MM) metadynamics to unravel the catalytic mechanism of this retaining enzyme at the atomic-electronic level of detail. Our study provides a detailed structural rationale for an ordered bi-bi kinetic mechanism and reveals critical aspects of substrate recognition, which dictate the specificity for acceptor Thr versus Ser residues and enforce a front-face SN i-type reaction in which the substrate N-acetyl sugar substituent coordinates efficient glycosyl transfer.

Synthesis of new conformationally rigid phenylalanine analogues

Abstract The reactivity of (Z)-2-phenyl-4-benzylidene-5(4H)-oxazolone 1 as dienophile in the Diels-Alder reaction with 1,3-butadiene and 2,3-dimethyl-1,3-butadiene is studied. The adducts obtained starting from the cycloaddition of 1 with both dienes are converted, through simple reactions into the conformationally restricted cyclic amino acids cis-1-amino-2-phenylcyclohexanecarboxylic acid 6 and 1-amino-c-4,c-5-dimethyl-t-2-phenyl-r-1-cyclohexanecarboxylic acid 10 , analogues of phenylalanine.

SYNTHESIS OF A NEW ENANTIOMERICALLY PURE CONSTRAINED HOMOSERINE

Abstract The use of the Diels-Alder reaction between 1,3-butadiene and chiral 2-acetamidoacrylates as the key step followed by stereocontrolled transformations allows the synthesis of (1 S , 3 R )-1-amino-3-hydroxycyclohexanecarboxylic acid, a new type of constrained homoserine, with an excellent overall yield.

New synthesis of 7-azabicyclo[2.2.1]heptane-1-carboxylic acid

Abstract This report describes a new synthetic route to 7-azabicyclo[2.2.1]heptane-1-carboxylic acid (Ahc), a constrained proline analogue, in which the key step is the Diels–Alder reaction using methyl 2-benzamidoacrylate as dienophile.

Asymmetric synthesis of all isomers of α-methyl-β-phenylserine

Abstract This report describes the synthesis of enantiomerically pure (2 R ,3 R )-, (2 R ,3 S )-, (2 S ,3 S )- and (2 S ,3 R )-2-amino-3-hydroxy-2-methyl-3-phenylpropanoic acids, four quaternary α-amino acids, using a stereodivergent synthetic route and starting from ( S )- and ( R )- N -Boc- N , O -isopropylidene-α-methylserinals. The key step involves the asymmetric Grignard additions to the above chiral aldehydes, in which high levels of asymmetric induction are observed.

A straightforward synthesis of both enantiomers of α-vinylalanine and α-ethynylalanine

Abstract This report describes the synthesis of enantiomerically pure ( S )- and ( R )-α-vinylalanines and ( S )- and ( R )-α-ethynylalanines, four quaternary α-amino acids, using a straightforward synthetic route and starting from ( S )- and ( R )- N -Boc- N,O -isopropylidene-α-methylserinals.

Dynamic interplay between catalytic and lectin domains of GalNAc-transferases modulates protein O -glycosylation

Protein O-glycosylation is controlled by polypeptide GalNAc-transferases (GalNAc-Ts) that uniquely feature both a catalytic and lectin domain. The underlying molecular basis of how the lectin domains of GalNAc-Ts contribute to glycopeptide specificity and catalysis remains unclear. Here we present the first crystal structures of complexes of GalNAc-T2 with glycopeptides that together with enhanced sampling molecular dynamics simulations demonstrate a cooperative mechanism by which the lectin domain enables free acceptor sites binding of glycopeptides into the catalytic domain. Atomic force microscopy and small-angle X-ray scattering experiments further reveal a dynamic conformational landscape of GalNAc-T2 and a prominent role of compact structures that are both required for efficient catalysis. Our model indicates that the activity profile of GalNAc-T2 is dictated by conformational heterogeneity and relies on a flexible linker located between the catalytic and the lectin domains. Our results also shed light on how GalNAc-Ts generate dense decoration of proteins with O-glycans.