Nuclear Overhauser effect spectroscopy (NOESY) gave full assignments of the 1H‐NMR spectra of the picrotoxane neurotoxins tutin, hyenanchin, picrotoxinin and picrotin, as well as the solution conformations of these compounds, consistent with molecular modelling. Fully assigned 13C‐NMR data are reported. Copyright © 2001 John Wiley & Sons, Ltd.

(2.2 -Dimethyl bicyclo 12.2.1 J hept-3-ylmet hyl) phosphinic acid ( R PO,H,) , readily prepared from camphene and hypophosphorous acid, formed a polymeric calcium salt [{Ca( RPO,H),( RPO,H,) ( H20)}J, with both terminal and triply bridging phosphinate groups, and an overall columnar structure with an inorganic core and a pseudo-close-packed sheath of terpene moieties.The self-assembly of novel nanostructures using metal phosphates, phosphonates and phosphinates is an area of significant current interest, since such materials have applications in catalysis, ion exchange and sorptive processes. Specific examples include molecular sieve alumino-and gallo-phosphates, layered phosphonates having the ability to undergo shapeand enantio-selective ' intercalation reactions, and a vanadium phosphate which adopts a novel chiral double-helix structure.8 To date, however, studies have been largely restricted to salts of relatively simple, sterically non-demanding organophosphorus acids.We recently reported the high-yield synthesis of the phosphinic and phosphonic acids, RP02Hz 1 and RP03H2 2 respectively (R = 2,2-dimethylbicyclo[2.2.l]hept-3-ylmethyl), from inexpensive camphene (2,2-dimethyl-3-methylenebicyclo-C2.2. llheptane) and hypophosphorous (phosphinic) acid H3P02.9 Unfortunately, the attempted preparation of chiral 1 starting from (Rj( +)-camphene yielded only racemic material, as a result of acid-catalysed racemisation of the camphene; the structural stability of the RH skeleton (compared to that of the parent camphene) does however suggest that optical resolution of the enantiomers of 1 and/or 2 may be possible. The ready availability of these new organophosphorus acids suggested that metal derivatives having both novel structures and potential for materials separations (including ultimately enantioselective separations) might be accessible. We wished to undertake preliminary investigations into the structural chemistry of such metal phosphinate salts, and some of these studies are presented here.Reaction of the compound ( k )-1 t with 0.5 mol equivalent of Ca(NO3),.4HzO and an excess of urea (for pH control) for 5 d yielded a colourless solution which, upon slow evaporation, afforded colourless prismatic crystals. 1 These were characterised as the polymeric calcium salt [{Ca(RP02Hj2(RP02H2)-(H20)}J on the basis of a single-crystal X-ray study. § Owing to the relatively poor quality of the crystals, and the disorder of the R groups, arising from librational effects and possibly also from superposition of (+) and (-) enantiomers, the structure 7 Obtained by a modification of the previously reported route' by treating camphene with H,P02 (3 mol equivalents) in refluxing Pr'OH with a catalytic amount of benzoyl peroxide. The ( f )-phosphinic acid 1 has been fully characterised by NMR spectroscopy, electrospray mass spectrometry and by a single-crystal structure, full details of which will appear elsewhere.1 A solution of Ca(N03),.4H,0 (0.585 g, 2.48 mmol) with compound ( k )-1 (1 .OO g, 4.95 mmol) and urea (1.5 g, exc...

The reactions of cis-[PtCl 2 L 2 ] [L = PPh 3 , PMe 2 Ph or L 2 = Ph 2 P(CH 2) 2 PPh 2 (dppe)] with endo-8-camphanylphosphonic acid (CamPO 3 H 2) and Ag 2 O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O 3 PCam)L 2 ]. The X-ray crystal structure of [Pt(O 3 PCam)(PPh 3) 2 ]•2CHCl 3 shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh 3 ligands. This allows the O 3 P-CH 2 group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates nonfluxional behaviour for the sterically bulky PPh 3 and dppe derivatives, which contain inequivalent phosphine ligands in their 31 P NMR spectra. These findings are backed up by theoretical calculations on the PPh 3 and PPhMe 2 derivatives, which show respectively high and low energy barriers to rotation of the camphanyl group in the PPh 3 and PPhMe 2 complexes. The X-ray crystal structure of CamPO 3 H 2 is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.

No abstract