Biomedical subjects

Xavier Ariza

Publications and source records attributed to Xavier Ariza.

9 recordsLinked to original sources

PubMed2007

Collision-induced dissociation of cytidine and its derivatives.

The collision-induced dissociation of adenosine, uridine and guanosine, and their corresponding nucleobases has been published previously.1-3 Here we report the collision-induced dissociation of cytidine and the elucidation of its fragmentation pathways using stable isotope-labeled cytidines, through a quadrupole ion trap for tandem mass spectrometry up to MS(4). Furthermore, we investigated the collision-induced dissociation of five cytidine derivatives: 3-methylcytidine, N(4)-methyl-2'-deoxycytidine, 5-methylcytidine, 2-thiocytidine and N(4)-acetylcytidine. The primary fragmentation pathway was the neutral loss of ribose. MS(3) on the retained nucleobase generally resulted in an intense signal from the elimination of ammonia, but also in fragment ions characteristic of the different cytosine derivatives. On the basis of the MS(n) data, fragmentation pathways and plausible mechanisms are suggested.

Cytidine↗

PubMed2006

1-phenylprop-2-ynyl acetate: a useful building block for the stereoselective construction of polyhydroxylated chains.

(R)- or (S)-1-phenylprop-2-ynyl acetate was added stereoselectively to aldehydes to afford 4-hydroxy-1-phenylalk-2-ynyl acetates. The transformation of such adducts into the corresponding allylic 1,4-diacetates allowed a highly efficient transfer of chirality from C1 to C3 by a regio- and stereoselective [3,3]-sigmatropic rearrangement. The obtained unsaturated 1,2-diacetates were useful synthetic intermediates whose double bond and/or phenyl group were transformed in different aldehydes, acids, or esters.

Journal Article↗

PubMed2005

A novel nucleophilic approach to 1-alkyladenosines. A two-step synthesis of [1-15N]adenosine from inosine.

A novel ANRORC mechanism in the reaction of 1-(2,4-dinitrobenzenesulfonyl)inosines with amines has allowed the preparation of 1-alkyladenosines and [1-15N]adenosines in a straightforward way from inosines.

Adenosine↗

PubMed2005

[N,1-(15)N2]-2'-deoxyadenosines.

[reaction: see text] An efficient route to deoxyadenosine derivatives labeled on both the amino group and nitrogen 1 is uncovered. First, 3',5'-di-O-acetyl-2'-deoxy-1-(2-nitrobenzenesulfonyl)inosine (2a) and only 1.1 equiv of (15)NH4Cl are used for labeling position 1 (1a) through the isolation of the open intermediate and its cyclization with DBU in anhydrous CH3CN. Inosine 1a is then converted to [N,1-(15)N2]-3',5'-di-O-acetyl-N6-benzoyl-2'-deoxyadenosine (5a, the precursor of 6a) via a Pd/dppf-catalyzed chloride-to-benzamide replacement, by using again only 1.1 equiv of the labeling source.

Catalysis↗

PubMed2004

A straightforward synthesis of (-)-phaseolinic acid.

A concise approach to (-)-phaseolinic acid starting from commercially available (S)-oct-1-yn-3-ol is disclosed. The key steps are a ring-closing metathesis reaction to prepare a C(2)-symmetrical allylic diol and its desymmetrization to a gamma-butyrolactone by using an Ireland-Claisen rearrangement. The 2S,3S,4S configuration of the levogyre natural product has been confirmed.

4-Butyrolactone↗

PubMed2004

An efficient, stereoselective approach to syn-1,2-diols protected as cyclic carbonates.

Enantioenriched 4-hydroxyalk-2-ynyl carbonates (or benzoates) have been prepared by stereoselective zinc-mediated addition of alkyl 2-propynyl carbonates (or their benzoate analogues) to aldehydes. Their partial reduction to Z-olefins followed by cyclization under mild Pd-catalyzed conditions allowed a straightforward access to enantioenriched syn-1,2-diols protected as cyclic carbonates.

Journal Article↗

PubMed2004

A direct, efficient method for the preparation of n6-protected 15n-labeled adenosines.

N6-Protected adenosines have been prepared from inosines by activation of the C6 position and Pd-catalyzed coupling with amides. An efficient route to [6-15NH2]-N6-benzoyladenosine and [1-15N,6-15NH2]-N6-benzoyladenosine has been achieved.

Adenosine↗

PubMed2004

Highly stereoselective approach to alk-2-yne-1,4-diols by oxazaborolidine-mediated reduction of alk-2-yne-1,4-diones.

We performed the borane-mediated reduction of a series of symmetrical alk-2-yne-1,4-diones (5) in the presence of the oxazaborolidine (R)-6 to afford (R,R)-alk-2-yne-1,4-diols ((R,R)-1) in good yields and high stereoselectivities (up to 99.9% ee). In some cases, the stereochemical purity of 1 was improved by a two-step process: (i) temporary transformation of 1 into its vic-dibromo derivatives 9, which allowed us to remove the minor meso isomer by chromatography, and (ii) regeneration of the enantioenriched diols 1 with SmI2. Reduction of the hexacarbonyldicobalt complexes 8 derived from 5 was also successful.

Journal Article↗

PubMed2002

Stereodivergent approach to beta-hydroxy alpha-amino acids from C(2)-symmetrical alk-2-yne-1,4-diols.

[reaction: see text] A new stereodivergent route to erythro- and threo-beta-substituted serines from a common C(2)-symmetrical alk-2-yne-1,4-diol is described. Stereocontrol in such an acyclic system is achieved by taking advantage of symmetry. Stereoselective alkyne reduction to either (Z)- or (E)-olefin allows selection of the stereochemistry of alpha-carbon in the final amino acid by using a Pd(0)-catalyzed process. This strategy has been applied to the synthesis of (2S,3S)-3-hydroxyleucine.

Amino Acids↗