Impurities of tazarotene: isolation and structural characterisation.

Two impurities showing structures 5 and 6 were isolated and characterised by means of NMR analysis, during the optimisation of a synthetic procedure to tazarotene. Impurity 5, i.e.

Isolation and characterisation of a phenolic impurity in a commercial sample of duloxetine.

A phenolic impurity of duloxetine hydrochloride was isolated and characterised (MS, NMR, X-ray-analysis).

Isolation and characterisation of impurities in adapalene.

Three impurities of structure 2-4 were isolated and characterised during the optimisation of a synthetic procedure to adapalene. Impurity 1 was a by-product of the Friedel-Crafts reaction of adamantanol with 4-bromoanisole. Impurities 3 and 4 were due to side reactions of the final Negishi coupling.

Determination of the synthetic origin of methamphetamine samples by 2H NMR spectroscopy.

Samples of methamphetamine, prepared according to the most common synthetic pathways, were submitted to natural-abundance 2H NMR spectroscopy. The deuterium content at the various sites of the molecule was found to depend on its synthetic history. The technique provides a chemical fingerprint of methamphetamine samples and can give hints to trace back the starting materials and the synthetic procedures.