Mass spectroscopy of natural products. XXIII,Comparative positive and negative ion mass spectral studies of scapanin-type diterpenoidst

The mass spectral behaviour of 15 scapanin-type diterpenoids (8α,12-epoxylabdanes) was elucidated using accurate mass measurements and deuterium-labelled derivatives. The results obtained allow a localization of the functional groups in the diterpenoid system. Furthermore, the negative ion mass spectra of the scapanin-type diterpenoids are discussed and compared with the positive ion spectra.     

Solid-phase domino syntheses of functionalized tetronates with Ph3PCCO

Domino addition-Wittig olefination reactions of α-hydroxy esters immobilized on polystyrene with Ph₃PCCO to give resin-bound tetronates proceed as readily as in solution. α-Hydroxy allyl esters can react to give either supported allyl tetronates or the corresponding Claisen-rearranged 3-allyltetronic acids, depending on conditions.     

Ammonia detection via integrated optical evanescent wave sensors

Detection of ammonia in the gas phase by means of integrated optical components, coated with sensitive films which reversibly change their spectral absorption with ammonia concentration, is demonstrated. The evanescent wave of the guided light continuously probes the absorbance of the sensor membrane at 633 nm. The output intensity is compared with that of a reference channel not influenced by the sensitive film. With Bromocresol Green and Bromophenol Blue in silicone as indicators, ammonia levels of less than 1 ppm are detectable, the dynamic range being from 1 to 200 ppm. The response depends on the relative humidity, and acidic gases including sulphur dioxide, carbon dioxide, and nitric oxides are found to reduce the relative signal change caused by ammonia, whilst in the absence of ammonia they remain inert. Aging of the film is observed within a few months after film preparation.     

Platinum(II) Mixed Ligand Complexes with Thiourea Derivatives,Dimethyl Sulphoxide and Chloride: Syntheses,Molecular Structures,and ESCA Data

The platinum(II) mixed ligand complexes [PtCl(L^1‐6)(dmso)] with six differently substituted thiourea derivatives HL, R₂NC(S)NHC(O)R′ (R = Et, R′ = p‐O₂N‐Ph: HL¹; R = Ph, R′ = p‐O₂N‐Ph: HL²; R = R′ = Ph: HL³; R = Et, R′ = o‐Cl‐Ph: HL⁴; R₂N = EtOC(O)N(CH₂CH₂)₂N, R′ = Ph: HL⁵) and Et₂NC(S)N=CNH‐1‐Naph (HL⁶), as well as the bis(benzoylthioureato‐κO, κS)‐platinum(II) complexes [Pt(L^{1, 2})₂] have been synthesized and characterized by elemental analysis, IR, FAB(+)‐MS, ¹H‐NMR, ¹³C‐NMR, as well as X‐ray structure analysis ([PtCl(L¹)(dmso)] and [PtCl(L^{3, 4})(dmso)]) and ESCA ([PtCl(L^{1, 2})(dmso)] and [Pt(L^{1, 2})₂]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square‐planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the Pt^II atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt—S‐bonds to the DMSO are significant shorter than those to the thiocarbonyl‐S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p‐NO₂, o‐Cl) cause a significant elongation of the Pt—S(dmso)‐bond trans arranged to the benzoyl‐O—Pt‐bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f_7/2 electron binding energies of the complexes [PtCl(L^{1, 2})(dmso)] are higher than those of the bis(benzoylthioureato)‐complexes [Pt(L^{1, 2})₂]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands.     

Zur Reaktion von Derivaten des Thiosemicarbazids mit Bisimidchloriden der Oxalsäure

Summary Arylsubstituted oxalic bis-imidochlorides1 react with thiosemicarbazones of type5 as well as13 to give five-membered-ring heterocycles8,11, and16.¹³C-NMR spectroscopy, chemical methods and X-ray crystallography have been used to investigate the nature of the structures obtained. The¹³C-chemical shifts of13 and imidazolidines16 are correlated with Hammett _p constants and dual substituent parameters to evaluate the transmission of theX substitutent electronic effects via the side-chain iminyl carbon atom into the heterocyclic ring and its neighbouring phenyl groups.