No abstract

We have developed QUANTAS (QUANTification by Artificial Signal), which is a software-based protocol for concentration measurement by NMR. QUANTAS is an absolute intensity external standard method for quantification by NMR that compensates for various experimental parameters. It is applicable to all nuclei and modern spectrometers. QUANTAS is demonstrated here for (1)H and (19)F NMR, enabling heteronuclear integrals to be compared. It can be applied using fixed probe tuning, matching and pulse length, for samples with the same effective loading on the probe coil as the appropriate reference spectrum. Otherwise, an optimised tuning and matching approach is adopted for every sample together with explicit PULCON (PUlse Length-based CONcentration measurements) absolute intensity corrections.

Universal quantitative detection without the need for analyte reference standards would offer substantial benefits in many areas of analytical science. The quantitative capability of high-performance liquid chromatography (HPLC) with charged aerosol detection (CAD) was investigated for 50 compounds with a wide range of physical and chemical properties. It is widely believed that CAD is a mass detector. Quantification of the 50 compounds using a generic calibrant and mass calibration achieved an average error of 11.4% relative to 1H NMR. Correction factors are proposed that estimate the relative surface area of particles in the detector, taking into account the effects of the density and charge of analytes. Performing these corrections and quantifying with surface area calibration, rather than mass, shows considerably improved linearity and uniformity of detection, reducing the average error relative to 1H NMR to 7.1%. The accuracy of CAD quantification was most significantly improved for highly dense compounds, with traditional mass calibration showing an average error of 34.7% and the newly proposed surface area calibration showing an average error of 5.8%.

No abstract

A new class of prostanoid has been synthesized. The carboxylic acid ester (3) is an analogue of prostaglandin J, and contains an allene moiety at C,*. The novel compound (3) is available from 7-chloronorbornadiene (5) in a route which has t w o key steps. The first is the reaction of ( 5) with an alkynyl Grignard reagent to give the dienyne (7). The second is the regioseloctive epoxidation of the dienyne ( 7 ) , rearrangement of the epoxide (8) to give the aldehyde (9), followed by an oxa-Cope rearrangement; the derived enol (10) was hydrolysed to give the useful prostaglandin synthon ( 14) directly.In view of the current interest in prostaglandin J, (PGJ,) (1) and related compounds [e.g. (2)] ' as anti-neoplastic agents against a variety of tumour types, we wish to report a short flexible route to the allene (3) (Scheme).