Afin de connaitre avec prkcision l'influence du pontage sur la conformation du squelette heptahClicCnique, nous avons CtudiC, par diffraction des rayons X, les composCs suivants : [7]htlickne, dimCthyl-3,15-[7]hClicene (lo), hClidne (
This paper describes the structure determinations of two new ichthyotoxic bia-quino-The structural elucidalitidhe alkaloids from the marine sponge Petmeia eel.iata. tions are w a t l y based on hanonuclear 2D-'H NlIR experiwnta. the middle of the 16-meabered ring and perpendicular to the mean plane of the same ring(3). Accordingly. although petrosin (2) is a C~o-molecule only 15 peaks are observed in the proton noise-decoupled "C NMR apectrum. Petrosin -A (1) behaves in the same way. shoving 15 peaks in the "C NHR spectrum and only one 6H doublet at 6 0.96 attributable to the tvo methyl groups, in the 'H NHR spectrum. This indicates that 2 also has a tvo-fold rotation axis. contrast. petrosin -B (2) has no element of symmetry. ristic seriea of IR bands betveen 2700 and 2850 m-' (Bohlmann bands). in accordance vith a tnme-fumed ring conformation for the quinolizidine systems(4). The equatorial position of the methyl groups i n 2 and 2 follovs from the comparison of their 'H and "C chemical shifts and J3-16 coupling constants vith thole of (see table I and 2 ) . Axial methyl groups should The latter is racemic and possess a tvo-fold rotation axis (Cz) passing through In A l l three alkaloids exhibit a characte-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.