J. P. Declercq

Chemical studies of marine invertebrates. XLI. Sigmosceptrellin-A methyl ester a nor-sesterterpenoid peroxide from the sponge sigmosceptrella laevis.

Abstract Structure 1 has been established for sigmosceptrellin-A methyl ester, a novel ichtyotoxic nor-sesterterpenoid from the sponge S. laevis.

Crystal and molecular structure of bis(β-alanine) zinc nitrate tetrahydrate. electron spin resonance and optical studies of copper(II) diluted in this compound.

Abstract The structure of the title compound has been established by three-dimensional X-ray crystal structure analysis from diffractometer data. Crystals are monoclinic, space group P2 1 / n , with a = 23.891, b = 6.576, c = 5.519 A , β = 95,67°, Z = 2. The structure was solved by direct methods (MULTAN) and refined by least-squares calculations to R = 0.042 for 886 independent reflexions. The zinc atom coordination in the centrotymmetric cation is octahedral with Zn-O(ala) 2.072 and Zn-O(water] 2.082 and 2..165 A . ESR and optical studies reveal that copper(11) substitutes the Zinc ions in the host matrix, the local symmetry around Cu being at most C 2h . The experi- mental g and hyperfine values (g 1 = 2.400. g 2 = 2.097, g 3 = 2.084; A 1 = 0.0135, A 2 = 0.0022. A 3 = 0.0024 cm −1 ) could be reproduced within a crystal field model incorporating orbital reduction factors (k z = 0.875, k x = 0.860, k y , = 0.860). M.O. coefficients are roughly estimated.

Chemical composition of the frontal gland secretion from soldiers of nasutitermes lujae (termitidae, nasutitermitinae)

Abstract The front gland secretion of soldiers of the West African Nasute termite Nasutitermes lujae contains the monoterpene terpinolene 1, and five diterpenes, four of them (5 to 8) belonging to the trinervitane skeleton while the fifth (3) is a secotrinervitane derivative. 3 and 8 are new derivatives whose structure has been established by chemical correlation and by X-ray diffraction analysis respectively.

Synthese et structure par diffraction de rayons x de la dihydro-3,12 tetramethyl-3,3,6,12 7H-pyranno[2,3-c]acridinone-7

Abstract The synthesis of 3-hydroxy-1,10-dimethyl-9-acridone XIII, via the initial condensation of methyl anthranilateVI and orcinol VIII in presence of heptanol and ptolylsulfonic acid, is described. The condensation of XIII with 3-chloro-3-methylbut-l-yne afforded 3,12-dihydro-3,3,6,12-tetramethyl-7H-pyrano [2,3-c]acridin-7-one II. The structure of II has been established through the use of a study by X-ray diffraction.

Anchoring Substitution in Acyclic 1,3-amino Alcohols - Asymmetric Reductions With Chiral Modifications of Lithium Aluminum-hydride and Borane

Chiral modifications of LAH and amino alcohols 1b and 2 give erratic results in the asymmetric reduction of acetophenone. In the presence of chiral tetrahydro-1,3,2-oxazaborines, derived from 1a, however, the borane reduction of acetophenone consistently leads to the (R)-carbinol in excess. The absolute configuration of the chiral ligands is determined via X-ray analysis of the ammonium (S)-(+)-10-camphorsulfonate salt 8, derived from 2.

An eight-membered ring containing two phosphorus atoms. trans isomer of 2,6-dimethyl-1,3-dioxa-2,6-diphosphacyclooctane 2,6-disulphide

C6H]402P2S 2 is monoclinic, P2]/n, with Z = 4, a = 9.954(2), b = 9.632(1), c = 12.165(1)A, fl = 102.31 (1) °, D c = 1.42, O m -1-40 (2) Mg m -3. 2012 independent reflexions were collected on a Syntex computer-automated diffractometer. The structure was solved by direct methods using the MULTAN system. A final R value of 0.037 was obtained for 1770 reflexions with I > 2.5o(1). The eight-membered ring adopts an asymmetric boat-chair conformation. The bond lengths and bond angles are compared to those obtained on cyclic 2-methyl-2-thioxo-l,3-dioxa compounds of various ring size.

Pseudoguaianolides: a stereoselective approach to 8(α)-oxygenated helenanolides. X-ray structural determination of a synthetic intermediate.

Abstract The synthesis of perhydroazulenic lactone 8 , a potential precursor for several helenaholides is described. Its structure is determined by X-ray diffraction of the corresponding alcohol 9 .

Structures de la dihydro-4,5 diphényl-1,8 3H-pyrrolo[1,2-d][diazépine-1,4] et du perchlorate de dihydro-4,5 diphényl-1,8 7H-pyrrolo[1,2-d][diazépinium-1,4]

The structures of 4,5-dihydro1,8-diphenyl-3 H-pyrrolo[1,2-d][1,4]diazepine (DDPD), C20HIaN2, and the perchlorate of its protonated form (DDPDH ÷. CIO4), C20HI9N+.C104, have been solved by direct methods (MULTAN) from diffractometer data. DDPD is monoclinic, P21, with a = 11.894 (2), b = 7.544 (1), c = 9.926 (2) A, fl = 120.41 (1) ° and Z = 2 for D x = 1.24 Mg m -3, V 768.11 /~k 3. DDPDH +. C10 4 is monoclinic, C2/c, with a = 16.662 (7), b = 8.158 (2), c = 28.124 (14) A, ~ = 104.41 (4) ° and Z = 8 for D x = 1.39 Mg m -3, V = 3702.59 A 3. X-ray analysis proves that the acid-base interconversion products form two distinct delocalized systems.

Identification and structure of 2-chloro-2-phenoxymalonylamide-amidinium hydrochloride monohydrate

The structure of C13H19N302C12. H20 has been obtained by X-ray diffraction methods. The crystals are monoclinic, space group P21/c, with a=8-871 (1), b=25.898 (2), c=7.963 (1),~,, fl= 113.54 (1) °, and Z = 4. The structure was solved by direct methods and refined by block-diagonal least-squares calculations to an R of 0-046. The molecules are held together by a one-dimensional array of hydrogen bonds extending in the a direction. A short N H . . . O intramolecular distance is thought to participate in a bifurcated hydrogen bond.

X-ray crystallographic analysis of 2-acetylimino-3-isopropyl-5-methyl-4-phenyl-2,3-dihydro-1,3-thiazole

The crystal structure determination of C15H18N2OS allows the unambiguous identification of the reaction product of an alpha-bromoketimine with potassium thiocyanate.