Practical asymmetric synthesis of 1,2-diamines in the 3-aminoazepane series.

A simple and versatile method for the enantio- and diastereoselective synthesis of mono- or disubstituted 3-aminoazepanes is described. The key step involves a highly regio- and diastereoselective tandem ring-enlargement/alkylation or reduction process. This novel synthetic route provides enantiomerically pure constrained diamines interesting as scaffolds for medicinal chemistry.

Enantioselective desymmetrization of meso bicyclic hydrazines: a novel approach to the asymmetric synthesis of polysubstituted amino cyclopentanic cores.

Catalytic asymmetric hydroboration can be successfully applied to meso bicyclic hydrazines. The resulting alcohols are of great synthetic interest and can lead in a straightforward manner to cyclopentanic diamino alcohols with good enantiomeric purity.

Synthesis, modelling and NK1 antagonist evaluation of a non-rigid cyclopropane-containing analogue of CP-99,994.

A non-rigid cyclopropane-containing diamine analogue of CP-99,994 was synthesised and was found to have only moderate NK1 receptor binding affinity. Molecular dynamics calculations of the conformational space of the former compound gave good correlation between observed activity and a recently published pharmacophore model, lending predictive value to the latter.

Synthesis of enantiomerically pure alpha-substituted propargylic amines by reaction of organoaluminum reagents with oxazolidines.

Various oxazolidines prepared in two steps from (R)-phenylglycinol react at 0 degrees C with dialkylalkynylalane-triethylamine complexes in the presence of trimethylaluminum in high yield and diastereoselectivity. Enantiomerically pure primary alpha-substituted propargylamines can be easily obtained in two steps after removal of ferrocenylmethyl protective group under smooth acidic conditions and oxidative cleavage of the chiral appendage.

Quantitative high-performance liquid chromatographic determination of acrolein in plasma after derivatization with Luminarin 3.

A rapid, sensitive and specific high-performance liquid chromatographic method for the quantification of acrolein (1), one of the toxic metabolites of oxazaphosphorine alkylating agents (cyclophosphamide and ifosfamide) was developed. Condensation of acrolein with Luminarin 3 afforded a fluorescent derivative that could be specifically detected and quantified. Chromatographic conditions involved a C18 RP column Uptisphere and a gradient elution system to optimize resolution and time analysis. The method showed high sensitivity with a limit of detection of 100 pmol/ml and a limit of quantification of 300 pmol/ml. This technique is particularly suitable for pharmacokinetic studies on plasma of oxazaphosphorine-receiving patients.

Synthesis and conformational analysis of two 2-oxopiperazine-containing tetrapeptide analogues.

One unsubstituted and one stereoselectively prepared 3-(S)-substituted-2-oxopiperazine have been used as dipeptide templates to generate tetrapeptide analogues. NMR analysis shows that these tetrapeptide analogues present an inverse gamma-turn conformation in chloroform.

[Chirality and drugs]. / Chiralité et médicament.

Following a brief historical review of the notion of chirality, the importance of the relationship between pharmacological activity and the enantiomeric forms of drugs is indicated. Different approaches for the preparation of optically-pure molecules are discussed, and an original strategy, known as the "CN(R,S) method", is described. To conclude, an application of this method in the synthesis of a pharmacologically-active molecule is presented.

Alfalfa Root Flavonoid Production Is Nitrogen Regulated.

Flavonoids produced by legume roots are signal molecules acting both as chemoattractants and nod gene inducers for the symbiotic Rhizobium partner. Combined nitrogen inhibits the establishment of the symbiosis. To know whether nitrogen nutrition could act at the level of signal production, we have studied the expression of flavonoid biosynthetic genes as well as the production of flavonoids in the roots of plants grown under nitrogen-limiting or nonlimiting conditions. We show here that growth of the plant under nitrogen-limiting conditions results in the enhancement of expression of the flavonoid biosynthesis genes chalcone synthase and isoflavone reductase and in an increase of root flavonoid and isoflavonoid production as well as in the Rhizobium meliloti nod gene-inducing activity of the root extract. These results indicate that in alfalfa (Medicago sativa L.) roots, the production of flavonoids can be influenced by the nitrogen nutrition of the plant.

Two new alkaloids from Xestospongia sp., a New Caledonian sponge.

Five alkaloids have been isolated from a New Caledonian sponge Xestospongia sp. These include three known xestospongin derivatives, the new demethylxestospongin B (1) and a tetrahydrocarboline derivative 5. The structures of the new compounds 1 and 5 have been established by nmr studies and comparison with previously described products.

Comparative cytotoxicities of a series of ellipticine and olivacine derivatives on multidrug resistant cells of human and murine origins.

The MDR P-glycoprotein has been described as a major factor of multidrug resistance. This transmembrane glycoprotein acts like an energy dependent efflux pump which possesses a broad specificity. It seems to be acting as a pump requiring drug fixation prior to extrusion. With the aim of investigating which parameters influence the recognition of drugs by the MDR system, we have determined the toxicities of different drugs on human and murine sensitive and resistant cell lines. For this purpose we have isolated and characterized a human adriamycin-resistant cell line, CEM/Adr, which presents an MDR phenotype. The tested drugs were ellipticine and olivacine derivatives which differ through discrete lateral chain substitutions. The influence of lateral chain lipophilicity and nitrogen quaternarization on drug recognition was studied. Small modifications in the chemical structure of the drugs have induced large changes in their toxicities and in the cross-resistance levels of the MDR cells to the tested compounds. The cross-resistances of the murine and human cells to the various compounds were strikingly different. The validity of murine screening models in the selection of anti-tumor drugs for human therapy must therefore be questioned.

Synthesis and cytotoxic activity of hydroxylated derivatives of olivacine in relation with their biotransformation.

The chemical synthesis of 9-hydroxyolivacine and 7-hydroxyolivacine based on a biomimetic approach is described. These two hydroxylated derivatives have been found as main in vitro metabolites of olivacine after incubation with rat hepatic microsomes. The pretreatment of animals with benzo[a]pyrene caused a large increase in both microsomal hydroxylations, whereas the pretreatment with phenobarbital caused a weak increase, with a preservation of 9-hydroxylation/7-hydroxylation ratio greater than 1 in both cases. The two hydroxyolivacines have been also found as principal in vivo metabolites of olivacine in rat bile as glucuronide and sulfate conjugates. The pretreatment of animals with benzo[a]pyrene reverses the 9-hydroxyolivacine/7-hydroxyolivacine ratio excretion in bile to a value that is less than 1. In both in vitro and in vivo experiments, the free metabolites were identified by HPLC and UV-visible, MS, and 1H NMR spectra. Hydroxylation at position 9 increases the in vitro cytotoxicity against leukemia L1210 cells (ID50 = 0.06 microM compared to 2.03 microM for olivacine) and an opposite effect is observed for hydroxylation at position 7 (ID50 = 12.8 microM). On the other hand, hydroxylation at position 9 has no effect on the in vivo antitumor activity against L1210. This might be related to the oxidative and conjugative metabolic pathways that play an important role in antitumor activity and deactivation of olivacine and its hydroxy metabolites.

Melatonin synthesis by rabbit platelets.

Platelets of reserpinized rabbits, incubated in buffer containing tritiated 5-hydroxytryptamine (3H-5HT), have the ability to convert 3H-5HT into labeled compound(s) extractable with alkaline-chloroform. The bulk of the chloroform-extractable radioactivity showed a Rf value similar to authentic melatonin on silicagel thin-layer chromatography. The labelled product eluted with ethanol from the silicagel area where melatonin was suspected to reside was identified as melatonin by mass spectrometry and radioimmunoassay. Our in vitro experiments demonstrate that rabbit platelets are capable of converting 5-HT into melatonin apparently because they possess the enzymatic equipment necessary for this biosynthesis i.e. serotonin N-acetyltransferase and hydroxyindole-O-methyltransferase.

[Determination of structures by H NMR at 400 MHz: albifloranine, a new alkaloid from Tabernaemontana albiflora]. / Détermination de structures par RMN du 1H à 400 MHz: albifloranine, un nouvel alcaloïde de Tabernaemontana albiflora.

The structure of albifloranine 1, a new alkaloid of ibogane type from the stem bark of Tabernaemontana albiflora (M IQ.) Pull. (Apocynaceae) has been determined. A detailed (1)H NMR study of albifloranine 1, coronaridine 2 and heyneanine 3 is presented.