Biomedical subjects
Publications and source records attributed to Yves Gimbert.
Theoretical calculations at the DFT level indicate that the reaction of a nitrone with a silyl ketene acetal proceeds, contrary to previous suggestions, through a classical 1,3-dipolar cycloaddition, followed by a silyl group transfer step to give the open-chain product. Introduction of a diffuse basis set is necessary to describe properly nitrones. The influence of a Lewis acid has been studied.
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Internal energies and energy distributions were studied using the 'survival yield' method developed previously. In addition to conventional benzylpyridinium salts, protonated esters (fragmenting by rearrangement) and protonated leucine enkephalin were also used, extending the validity of the technique. Fragmentation processes were studied in the cone voltage region and modeled by the RRKM-based MassKinetics program. The results show that the shapes of the energy distributions are similar to thermal distributions. The mean internal energies are very similar for all compound classes studied, and show a linear increase with collision energy in the 10-50 eV region.
The reactivity of different Co(2)(CO)(6)-acetylene complexes in the Pauson-Khand reaction is strongly dependent on the nature of the olefin. Theoretical calculations at both the DFT and ONIOM levels are concordant with experimental observations and suggest how the olefin-cobalt interactions in the complex could have a major effect on the relative reactivity of the olefins. This study rationalizes for the first time the experimentally observed reactivity differences of cyclohexene, cyclopentene, and norbornene.
[reaction: see text]. The Magnus Pauson-Khand (PK) mechanism has been studied for the first time by electrospray ionization coupled to tandem mass spectrometry. It has been found that loss of CO from the PK complex precedes olefin coordination and insertion.
Protected (3R,4S)-N-Boc-3-hydroxy-4-methyl-4-phenylazetidin-2-one has been synthesized stereoselectively and used to esterify protected 10-desacetylbaccatin III to give, following removal of the protecting groups, novel C-3' methyl taxotere (docetaxel).
[reaction: see text] A potential route to the topoisomerase I inhibitor hypoxyxylerone is demonstrated by a highly convergent synthesis of the penta(O-methyl) derivative. The key step in the approach is an anionic homo-Fries rearrangement, little used to date in natural product synthesis and employed here for the first time with a dinaphthalenic substrate, to access the pentacyclic system of hypoxyxylerone.
Three chiral electron-deficient phosphine ligands, [(4R,15R)-,3-bis(trifluoromethanesulfonyl)perhydro-1,3,2-benzodiazaphosphol-2-yl]diethylamine, C(12)H(20)F(6)N(3)O(4)PS(2), (IIIa), [(4R,5R)-1,3-bis(trifluoromethanesulfonyl)perhydro-1,3,2-benzodiazaphosphol-2-yl]dimethylamine, C(10)H(16)F(6)N(3)O(4)PS(2), (IIIb), and bis[(4R,5R)-1,3-bis(trifluoromethanesulfonyl)perhydro-1,3,2-benzodiazaphosphol-2-yl]methylamine, (IV), as the chloroform solvate, C(17)H(23)F(12)N(5)O(8)P(2)S(4).0.98CHCl(3), have been prepared from (1R,2R)-N,N'-bis(trifluoromethanesulfonyl)-1,2-cyclohexanediamine and diethyl phosphoramidous dichloride, dimethyl phosphoramidous dichloride or methyl imidodiphosphorus tetrachloride. The pi-acceptor abilities of these new types of ligands have been evaluated by X-ray determination of the P-N bond lengths; it has been found that the most promising ligand is the bis(phosphine) (IV).
The synthesis of P-N-P bidentate ligands and the evaluation, based on IR and X-ray data, of their pi-acceptor properties in the complexes derived from phenylacetylene-dicobalt hexacarbonyl have been carried out. In addition, the reactivity of these complexes in the Pauson-Khand reaction has been examined.