Les systèmes biphasiques. 3. Alkylation des purines en catalyse par transfert de phase

Abstract

La méthylation de l'adénine en catalyse par transfert de phase fournit sélectivement la méthyl‐9 adénine (98%), tandis que sa benzylation conduit à la benzyl‐9 adénine comme produit majoritaire à cǒté de très faibles quantités de benzyl‐3 adénine. L'alkylation de la xanthine, de la théobromine et de la théophylline par la měme technique donne naissance aussi aux dérives N‐alkylés correspondants avec de hauts rendements à l'exclusion de tout autre régioisomere O‐alkylé. Cette technique d'alkylation constitue, tant par sa simplicité que par sa sélectivityé, une amélioration considerable des méthodes conventionnelles.

Mapping charged silver(i) adenine polymers, [Adx+ Agy−zH](y − z)+, via electrospray ionization tandem mass spectrometry experiments

“…All experiments were performed using a commercially available quadrupole ion trap mass spectrometer (Finnigan-MAT model LCQ, San Jose, CA) equipped with electrospray ionization (ESI) and recently modified to allow the introduction of neutral reagents via the helium background gas inlet line. 15 9-Methyladenine was synthesized via standard literature procedures 16 and all other compounds and reagents used were commercially available and used without further purification.…”

Position-Specific Isotope Analysis of Xanthines: A 13C Nuclear Magnetic Resonance Method to Determine the 13C Intramolecular Composition at Natural Abundance

“…It appears that the difficulty of substitution at position 1 of theobromine can be attributed to the electronic deactivation of the nitrogen in position 1 and the steric effect of adjacent carbonyl groups. To overcome these difficulties, we relied on the method of alkylation phase transfer catalysis, 30 in which N- Table 3. Mean Isotopic Composition δ 13 C i (‰) and Standard Deviation (SD, ‰) Determined for Caffeine Obtained by the NMethylation of Commercial Theobromine with Three Yields and with Duplicates at Optimum Yield (75%) methylation with dimethyl sulfate is enhanced by catalysis with tetrabutylammonium bromide (Figure 1).…”

Pentafluorobenzylation of O4-ethylthymidine and analogs by phase-transfer catalysis for determination by gas chromatography with electron capture detection

“…Ions were prepared by 70-eV electron ionization and accelerated at 10 kV unless noted otherwise. Figure 1 shows MS-II and the region between MS-I and MS-II incorporating the metal vapor furnace or gas inlet (Cls-I) for neutralization, the ion lens for deflection (Dfl-I) of unneutralized ions (in experiments to be reported a collision gas is introduced here separately for neutral dissociation) (26), the molecular beam for reionization (Cls-III), a second electrostatic ion deflector (Dfl-II), and a retractable channel electron multiplier (Mlt-I) for direct measurement of the neutral and ion beams. Oxygen was used as the reionization target (9, 27) at a pressure giving 50% transmittance of 0003-2700/86/0358-0348$01.50/0 © 1986 American Chemical Society…”