Search

The mode of incorporation of 2H from [3,3-2H2]cadaverine into lupanine (2) and 13α-hydroxylupanine (3) in Lupinusangustifolius was determined by 2H nmr spectroscopy. Lupanine carried deuterium at positions 4α, 4β, 8α, 8β, 13α, and 13β. These six sites were approximately equally enriched. Similarly, 13α-hydroxylupanine carried label approximately equally at five sites, 4α, 4β, 8α, 8β, and 13β. [3,3-2H2]Cadaverine was prepared by borodeuteride reduction in D2O of the p-toluene-sulfonylhydrazone of N-benzoylpiperid-4-one, followed by degradation of the resulting N-benzoyl[4,4-2H2]piperidine into 1,5-dibromo[3,3-2H2]pentane, conversion into 1,5-diphthalimido[3,3-2H2]pentane, and acid hydrolysis.

Summary Aeruginosins represent a group of peptide metabolites isolated from various cyanobacterial genera and from marine sponges that potently inhibit different types of serine proteases. Members of this family are characterized by the presence of a 2-carboxy-6-hydroxyoctahydroindole (Choi) moiety. We have identified and fully sequenced a NRPS gene cluster in the genome of the cyanobacterium Planktothrix agardhii CYA126/8. Insertional mutagenesis of a NRPS component led to the discovery and structural elucidation of two glycopeptides that were designated aeruginoside 126A and aeruginoside 126B. One variant of the aglycone contains a 1-amino-2-( N -amidino-Δ 3 -pyrrolinyl)ethyl moiety at the C terminus, the other bears an agmatine residue. In silico analyses of the aeruginoside biosynthetic genes aer A- aer I as well as additional mutagenesis and feeding studies allowed the prediction of enzymatic steps leading to the formation of aeruginosides and the unusual Choi moiety.

The H–D exchange of 17-oxosparteine (1b) has been studied under homoenolization conditions. We find that 1b undergoes H–D exchange at the bridgehead carbon C7 at 130 °C, but forcing conditions (240 °C) using the medium (CD3)3COK/(CD3)3COD are required to induce exchange at C11, C15, and other sites. C15-Ha exchanges only marginally faster than C15-Hc, indicating that the β-lactam carbanion is stabilized primarily by the dipolar effect of the amide group. Keywords: protium–deuterium exchange, 17-oxosparteine, homoenolization.