Diisothiocyanates as heterodienophiles or dipolarophiles in the presence of α‐thioxothioamides or mesoionic thiazoles

Reactions of α‐thioxothioamides ( 1 ) with diisothiocyanates were carried out in the hope of generating the N,N′‐bis(1,3‐thiazoline‐2‐thiones) ( A ). Although that purpose could not be achieved, we succeeded in preparing the monocycloadducts 7 from the phenylene‐1,2‐diisothiocyanate ( 4 ). The benzimidazole derivatives 8 and 9 were also characterized and a mechanism was assumed to account for this intramolecular process. On the other hand, the regioselective synthesis of the N,N′‐biimidazole ( 13 ) containing the phenylene bridge was performed by the treatment of the 5‐aminothiazolium chloride ( 2 ) with the diisothiocyanate ( 4 ) in a basic medium. The mesoionic derivative 13 probably arises from the monoimidazolium‐4‐thiolate ( 12 ) which was shown to react with the salt 2 under similar conditions to give the primary cycloadduct 14 as an intermediate towards the bis(imidazolium) ( 13 ). © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:617–624, 2001     

Addition of isocyanides to α‐(methylthio)‐benzylidenamidinium iodides: A surprising access to 2‐(dialkylamino)imidazoles and 3,5‐diamino‐2H‐pyrrolium salts

A number of 2‐(dialkylamino)‐5‐(methylthio)imidazoles 2 are obtained by treating the formamidinium iodides 1a,b with isocyanides R³ NC under mild conditions. Reduction of these species can occur in the reaction medium to furnish the corresponding imidazoles 3 . In some cases, double cycloaddition across the imine bond of starting salts 1 also provides the (azetidin‐1‐yl‐methylene)ammonium iodides 4 . Reactions with tert‐butyl and isopropyl isocyanides in refluxing acetonitrile convert the acetamidinium iodide 1c into the 3,5‐diamino‐2H‐pyrrolium salts 7 . Mechanisms are suggested to account for these ring‐closure processes. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:370–376, 2000     

One-Pot Synthesis of Phosphinylphosphonate Derivatives and Their Anti-Tumor Evaluations

This paper reports on the synthesis of new hydroxymethylene-(phosphinyl)phosphonates (HMPPs). A methodology has been developed to propose an optimized one-pot procedure without any intermediate purifications. Various aliphatic and (hetero)aromatic HMPPs were synthesized in good to excellent yields (53–98%) and the influence of electron withdrawing/donating group substitution on aromatic substrates was studied. In addition, the one-pot synthesis of HMPP was monitored by ³¹P NMR spectroscopy, allowing effective control of the end of the reaction and identification of all phosphorylated intermediate species, which enabled us to propose a reaction mechanism. Optimized experimental conditions were applied to the preparation of biological relevant aminoalkyl-HMPPs. A preliminary study of the complexation to hydroxyapatite (bone matrix) was carried out in order to verify its lower affinity towards bone compared to bisphosphonate molecules. Moreover, in vitro anti-tumor activity study revealed encouraging antiproliferative activities on three human cancer cell lines (breast, pancreas and lung).     

Improvement of the inverse-gated-decoupling sequence for a faster quantitative analysis of various samples by 13C NMR spectroscopy

The inverse-gated-decoupling sequence enables quantitative (1)H decoupled (13)C spectra to be obtained. We modified this sequence so as to obtain the same result in less time for molecules containing carbons with various relaxation properties. For that, we determined the optimal (13)C longitudinal-magnetization initial value for a faster relaxation while (1)H decoupler is stopped. This value can be calculated precisely via the nuclear Overhauser effects, the longitudinal relaxation times, together with the determination of the relaxation rate constants of carbons while (1)H are out of equilibrium. A supplementary delay of (1)H decoupling and/or a series of selective pulses applied at the beginning of the recovery delay allow an acceleration of (13)C longitudinal relaxation. We applied this method to the molecule of vanillin. The simultaneous quantification of all carbons was carried out with a recovery delay divided by two compared to the usual sequence.     

Correspondence rules and properties of smoothed phase space distribution functions

According to the link between phase space distribution functions and correspondence rules via an arbitrary weighting function, we show that a necessary and sufficient condition for obtaining a direct correspondence between a real phase space distribution function and the density operator of a pure state imposes the weighting function to be unimodular. The same condition is also shown to a particular case of interest for deriving a general formula from which previous known results such as orthonormality of phase space eigenfunctions, non-negativity of smoothed Wigner distributions or phase space interpretation of the scalar product are recovered as special cases.     

Random continued fractions and inverse Gaussian distribution on a symmetric cone

In this paper we introduce the inverse Gaussian and Wishart distributions on the cone of real (n, n) symmetric positive definite matricesH _n ⁺ () and more generally on an irreducible symmetric coneC. Then we study the convergence of random continued fractions onH _n ⁺ () andC by means of real Lagrangians forH _n ⁺ () and by new algebraic identities on symmetric cones forC. Finally we get a characterization of the inverse Gaussian distribution onH _n ⁺ () andC.     

Bisphosphonate prodrugs: synthesis of new aromatic and aliphatic 1-hydroxy-1,1-bisphosphonate partial esters

Methods for the preparation of various 1-hydroxy-1,1-bisphosphonate partial esters were developed. They were obtained from (alkyl or phenyl) bis(trimethylsilyl) phosphite and aromatic or aliphatic acid chlorides, followed by methanolysis.     

Total synthesis of the marine pyridoacridine alkaloid sebastianine A

The synthesis of the marine alkaloid sebastianine A and of a regioisomer has been accomplished via hetero-Diels-Alder reaction of indole-4,7-dione or N-tosylindole-4,7-dione with trifluoroacetamidocinnamaldehyde dimethylhydrazone, and subsequent cyclisation in alkaline conditions.