S. H. Simonsen

Terpenoids from Ageratina saltillensis

Abstract Twenty-two terpenoids were isolated from Ageratina saltillensis including eighteen new compounds, namely, 16-hydroxy-3,4β-epoxy-5β, 10β-cis-17α,20α-cleroda-13(14)-en-15,16-olide, 3α,4β,16-trihydroxy-5β,10β-cis-17α,20α-cleroda-13(14)-en-15,16-olide, 3α,4β-dihydroxy-5β,10β-cis-17α,20α-cleroda-13(14)-en-15,16-olide, 3α-methoxy-4β-hydroxy-5β,10β-cis-17α,20α-cleroda-13(14)-en-15,16-olide, 3-oxo-4β-hydroxy-5β,10β-cis-17α,20α-cleroda-13(14)-en-15,16-olide, 2β-hydroxy-3,4β-epoxy-5β,10β-cis-17α,20α-cleroda-13(14)-en-15,16-olide. 2β-hydroxy-5β,10β-cis-17α,20α-cleroda-3,13(14)-diene-15,16-olide, (13Z)-2β-hydroxy-5β,10β-cis-17α,20β-cleroda-3,13(14)-diene-15-oic acid, (13Z)-2-oxo-5β,10β-cis- 17α,20β-cleroda-3,13(14)-diene-15-oic acid, 3,4β-epoxy-5β-10β-cis-17α,20α-cleroda-15-oic acid, 16-hydroxy-3,4β-epoxy-5β,10β- cis-17α,20α-cleroda-15-ol, 8β-5′-[5″-hydroxytigloyloxy]-tigloyloxy-3-dehydro -4β,15-dihydrozaluzanin C, 8β-5′-[5″-hydroxytigloyloxy]- tigloyloxy-4β,15-dihydrozaluzanin C, 4′-desoxy-3-desacetoxy-3β-hydroxyprovincialin, 5′-[5″-hydroxytigloyloxy]- 5′-hydroxyheliangine, 3β-acetoxyliacylindrolide, 6-eudesmene-4α-ol and 6,15α-epoxy-1β,4β-dihydroxyeudesmane. The stereochemistry of one of the four known compounds, 3,4β-epoxy-5β,10β-cis-17α,20α- cleroda-13(14)-en-15,16-olide, has been revised by X-ray analysis. The stereochemistry of four compounds were established by NOE experiments.

(4,0)-Dirhodium(II) tetrakis[methyl 1-acetyl-2-oxoimidazolidine-4(S)-carboxylate]. Implications for the mechanism of ligand exchange reactions

Abstract The preparation and structural characterization of an elusive geometrical isomer of dirhodium(II) tetrakis[methyl 1-acetyl-2-oxoimidazolidine-4(S)-carboxylate], Rh2(4S-MACIM)4, has been achieved. The imidazolidinone ligands are arrayed around the dirhodium(II) core with four nitrogen donor atoms bound to one rhodium and four oxygens bound to the other (4,0). The crystal structure of this compound has been determined to be that of (4,0)-Rh2(4S-MACIM)4(CH3CN)2d(CH3CN): space group P2(in1) with cell constants a = 11.518(4), b = 16.851(2), c = 11.573(3) A , V = 2155.4(6) A 3 , Z = 2,R = 0.0295, RhRh distance = 2.4547(6) A . Prepared by ligand substitution on Rh2(OAc)4, (4,0)-Rh2(4s-MACIM)4 was isolated in 25% yield, but this compound isomerizes to its (2,2-cis)- and (3,1)-isomers under the reaction conditions. Racemic products were obtained from catalytic uses of (4,0)-Rh2(4S-MACIM)4 in diazo decomposition reactions.

Dirhodium(II) tetrakis[N,N-dimethyl-2-pyrrolidone-5(S)-carboxamide]. Structural effects on enantioselection in metal carbene transformations

Abstract The preparation and structural characterization of dirhodium(II) tetrakis[ N,N -dimethyl-2-pyrrolidone-5( S )-carb- oxamide], Rh 2 (5 S -DMAP) 4 , a new sterically-demanding catalyst for enantioselective metal carbene transformations, is described. The pyrrolidone ligands are arrayed around the dirhodium(II) core with two oxygen and two nitrogen donor atoms, each oriented cis , bound to each octahedral rhodium. The crystal structure of this compound has been determined to be that of Rh 2 (5 S -DMAP) 4 (CH 3 CN) 2 ·CH 3 CN·6H 2 O: space group P 2 1 2 1 2 1 with cell constants a = 12.685(4), b =15.050(3), c =24.035(4) A; V =4588.5(1.9) A 3 , Z =4, R =0.0316, RhRh distance =2 4538(5) A. Decreased activity for diazodecomposition catalyzed by Rh 2 (5 S -DMAP) 4 is observed, and enantiocontrol for cyclopropanation and carbon-hydrogen insertion is lower than expected by analogy to the corresponding di- rhodium(II) tetrakis[methyl 2-pyrrolidone-5( S )-carboxylate], Rh 2 (5 S -MEPY) 4 Electronic stabilization of the in- termediate metal carbene is absent in reactions catalyzed by Rh 2 (5 S -DMAP) 4 .

Crystal and molecular structures of (η6-xanthene)- (η5-cyclopentadienyl)iron(II) hexafluorophosphate and (η6-2-methylthianthrene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate

The crystal structures of the hexafluorophosphate salts of (η6-xanthene)(η5-cyclopentadienyl)iron (I) and (η6-methylthianthrene)(η5-cyclopentadienyl)iron (II) have been determined. The xanthene complex crystallizes in the triclinic system, space group P1, a 8.585(2), b 10.224(2), c 10.483(2) A; α 96.524(11), β 110.484(11), γ 101.836(9)°, V = 826.1(3) A3; Z = 2, 4218 reflections were refined to R = 0.046. The 2-methylthianthrene complex crystallizes in the orthorhombic space group P212121, a 11.526(2), b 11.940(10), c 13.701(10) A, V 1886(2) A3; Z = 4, 2278 reflections were refined to an R = 0.056. Both complexed heterocycles are bent and have dihedral angles between the planes of the phenyl rings of 176.71(9)° (xanthene) and 127.4(3)° (2-methylthianthrene). The stereochemistry of the double SNAr reaction leading to the formation of 2-methylthianthrene complex is discussed.

Sesquiterpene lactones, flavanones and a diterpene acid from Viguiera laciniata

Abstract The leaves and flower heads of Viguiera laciniata yielded lacinolide A, a new benzoic acid ester of heliangolide, and a new chlorinated heliangolide, lacinolide B, along with six other sesquiterpene lactones, four of which were new, one known diterpene acid and two known flavanones. The structures of all compounds were elucidated by NMR and mass spectroscopy. Lacinolide A was established by X-ray crystallography.

Conformational analysis of saturated heterocycles. Part 85. Perhydrodipyrido[1,2-b;1′,2′-e]-1,4,2,5-dioxadiazine

The title compound is shown to be the trans-isomer which exists both in the crystal (X-ray) and in solution (n.m.r) in the tetraequatorial conformation.

Crystal structure, and infrared and proton magnetic resonance spectra of 3-cyanomethylsulphonyl-2-morpholinocyclohexene : evidence for a C–H ⋯ N intramolecular hydrogen bond

The crystal and molecular structure of the title compound (1) has been determined from three-dimensional X-ray data by direct methods, and refined to R 0.038 for 2 263 independent reflections. Crystals are monoclinic a= 11.635(1), b= 9.315(1), c= 12.103(1)A, β= 93.00(1)°(at 23 °C), space group P21c, and Z= 4. A close C–H ⋯ N interaction, with H ⋯ N 2.47 A, is found between a hydrogen atom of the cyanomethylsulphonyl group and the morpholino-nitrogen atom. I.r. spectroscopic evidence confirms the existence of the interaction in the solid state, thus permitting it to be classified as a weak hydrogen bond. 1H N.m.r. and i.r. evidence indicates that the interaction may also exist in solution.

Synthesis, spectra, and crystal structure of 6,7,14,15-tetrahydrobis-benzimidazo[1,2-a;1′,2′-e][1,5]diazocine

2-[2-(4-Methylpyridinio)ethyl]benzimidazole (7a) and its 5,6-dimethyl derivative (7b) are converted by pyridine into cyclic dimers (8a and b), the spectra of which are described. An X-ray diffraction study of the tetrahydrobis-benzimidazodiazocine (8a) has verified the molecular structure.

Structure of an overcrowded molecule, benzylideneanthrone, at 193 K

The central six-membered ring of the anthrone in 10-bnzylidene-9(10H)-anthracenone assumes a boat conformation because of close interactions with the benzylidene moiety. Other manifestations of the overcrowding are the 6.1 o twist around the double bond, the -49.5 o rotation of the phenyl ring, and the increase of the C10a-C10-C11 angle to 124.1 o

Structure of (η5-cyclopentadienyl)(η6-thianthrene)iron(II) hexafluorophosphate

[Fe(CsI-I5)(C,2HsS2)][PFr] (I), M, = 482.22, monoclinic, P2Jc, a= 14.194 (3), b = 9.617 (2), c = 25-971 (5) A, /3 = 100.31 (2) °, V = 3488 (1) A3, Z = 8 (two molecules per a s y m m e t r i c u n i t ) , Dx = 1.836 g cm -3, Mo Kte (A = 0.70169 A), /z = 12-429 cm -1, F(000) = 1936, T = 163 K. Blockmatrix least-squares refinement of (I) converged to R = 0-044 and wR = 0.040 using 3785 reflections with I > 3g(/). The dihedral angles of the two molecules in the asymmetric unit are different. In molecule A, the FeCp moiety (Cp = cyclopentadiene) is inside the fold with a dihedral angle of 143.1 (2) °, whereas in molecule B, the FeCp moiety is located outside the fold with a dihedral angle of 136.3 (2) °. Introduction. In a continuation of our study on the synthesis, structure and properties of the FeCp complexes of tricyclic heterocycles, the structure of (I)