Porcine Kidney Diamine Oxidase (PKDO) was used to catalyse the oxidative transformation of Nitraria alkaloids. Nazlinin yielded indoloquinolizidine 4, an alkaloid which has been obtained as a natural product from Nitraria plant extracts. Oxidative deamination of 1-(4-butylamino)-beta-carboline 10 with PKDO yielded an unstable aldehyde (11), which cyclised to a new, arborescidine-type azepine (12). Addition of alcohol dehydrogenase during the oxidative deamination reduced the aldehyde in situ to the corresponding alcohol 13. Topaquinone-analogue 9 was effective as a stoichiometric oxidant for these primary amines. Characterisation of the enzyme reaction products was done by comparison with the chemically synthesised compounds. Copyright (C) 1996 Elsevier Science Ltd