A versatile and inexpensive electronic system for a high resolution NMR spectrometer

Abstract

The complete electronic system of a frequency-sweep 240 MHz NMR spectrometer working with a superconducting magnet is described. Full circuit and construction details are given for the rf sideband generator, pretuned coaxial cavity, af aperiodic synchronous detector, digital frequency synthesizer as well as a phase-coherent, variable-frequency, time-sharing pulse generator. This system, with multichannel irradiation possibilities uses extensively standard integrated logic circuits and can be inexpensively built by any laboratory engaged in NMR research.

Alcaloïdes bis‐indoliques de Catharanthus ovalis

“…L'analyse en haute resolution de son spectre de masse permet de lui attribuer [22] de la vincovalinine confirme la presence d'une partie vindoline liee par le C(10) a l'klkment R. I1 revele la presence de deux groupes mkthoxyle seulement (H,CO-C(11) et H3COOC-C(l6)). En plus de la resonance des six protons aromatiques on remarque a 6,lO ppm un signal d'un proton attribuable soit a un proton ethylenique, soit a H-C(16') [S] [23].…”

A UHF probe for NMR micro‐imaging experiments

“…During the past 20 years, a number of papers have been written on probes for highresolution proton NMR observations (1)(2)(3)(4)(5)(6)(7)(8). With the advent t of NMR imaging, special probes have been devised recently for whole-body, head, and micro-imaging experiments (9)(10)(11)(12).…”

Synthesis and behaviour under acidic conditions of 2-deoxy-D-arabino-hexopyranose and 3-deoxy-2-ketoaldonic acids bearing O-phosphono or O-glucosyl substituents at position β to the carbonyl function

“…The results obtained (Figure 3) suggested that release of inorganic phosphate was not entirely due to hydrolysis but to a p-elimination. There are at least three possible mechanisms (Scheme 1) which could explain the elimination of inorganic phosphate, each of which gives rise to the same compound : a 3,4-dideoxy-~-erythro-2-hept-3-enulosonic acid (21). At pH 2.6 the concentration of phosphate mono-anion is probably at its highest as are the rates of elimination (mechanisms I and 11) at this concentration (Figure 3).…”