Isolation and structure elucidation of genuine oat phytoalexin,avenalumin I

The major phytoalexin from oat leaves has been identified as 2-[2-(4-hydroxyphenyDethenyl] -6-hydroxy-4H-3,1-benzoxazin-4-one ($\text{A}$).     

Microwave—optical double resonance in the A1A2 excited state of thioformaldehyde

Microwave—optical double resonance experiments have been carried out on the 4_o¹ band of the $\text{A}$¹A₂$\text{X}$¹A₁ system of thioformaldehyde (H₂CS). More than 100 microwave and radiofrequency transitions have been observed in the $\text{A}$¹A₂ excited state. Many of these transitions are magnetically sensitive. Some of the excited state levels are perturbed by triplet levels and others by high vibrational levels of the ground state.     

Absolute stereostructures of halenaquinol and halenaquinol sulfate,pentacyclic hydroquinones from the okinawan marine sponge xestospongia sapra, as determined by theoretical calculation of CD spectra

The absolute stereostructures of two pentacyclic hydroquinones, halenaguinol ($\text{1}$) and halenaquinol sulfate ($\text{2}$) from the Okinawan marine sponge Xestospongia sapra, have been determined by means of theoretical calculation of CD spectra.     

Indole-alkaloid analogues from didroval tratum

The condensation products of secoaldehydes $\text{4}$ and $\text{16}$ with N-benzyl-tryptophane-methylester can be easily transformed into pentacyclic indole-alkaloid analogues.     

The rotational spectrum and molecular properties of a hydrogen-bonded dimer of phosphine and hydrogen fluoride

⁵⁷Fe Mössbauer spectra have been obtained for Fe(p-CH₃C₆H₄SO₃)₂ between 2.3 and 300 K in zero field, and at 2.3 and 4.2 K in longitudinal applied magnetic fields ranging from 1.1 to 5.6 T. The complex is a fast-relaxing paramagnet under all conditions studied and there is no evidence of antiferromagnetic exchange coupling. The FeO₆ chromophore is distorted by a trigonal elongation and the orbital ground state is the [($\text{2}\text{3}$)^{$\text{1}\text{2}$}|±2〉 ? ($\text{1}\text{3}$)^{$\text{1}\text{2}$}|?1〉] doublet. The temperature dependence of the quadrupole splitting has been analysed via a crystal-field model to provide estimates of the axial field splitting parameter Ds = -93 cm^-1, spin-orbit coupling constant λ = -70 cm^-1, and fine structure constant Dσ = -28 cm^-1. The magnetic properties of the complex are described by treating the ground state as a non-Kramers doublet with fictitious spin ? = $\text{1}\text{2}$. Five separate Mössbauer-Zeeman spectra can be fitted in this spin-hamiltonian approximation with identical values of the g- and A-tensor components, viz. g_⊥ = 1.0, g_u = 9.0; A_⊥ ≈ 2.0 mm s^-1. A_u = -1.79 mm s^-1. The trigonal z axis, the z axis of the electric field gradient tensor, and the easy axis of magnetisation are collinear, and the saturation value of the internal hyperfine field along this axis is +13.0 T.     

Studies on the synthesis of pentacyclic strychnos indole alkaloids. photocyclization of n-chloroacetyl-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole derivatives

Photocyclization of 2-chloroacetyl-1,2,3,4,5,6-hexahydro-1, 5-methanoazocino[4,3-b]indole ($\text{5}$) takes place at the indole 4-position to give a 1 ,2 ,3 ,4 , 5 ,6-hexahydro-2 ,11-ethano-1 ,5-methanoazocino [4 , 3-6] indole system. Consequently, the method appears to be unsuitable for constructing the pyrrolidine ring of pentacyclic Strychnos indole alkaloids.     

Synthesis of 3-methylisoguanosine,a positional isomer of pharmacologically active nucleosides from marine animals

3-Methylisoguanosine ($\text{4c}$) has been synthesized from 5-(cyanomethylamino)-1(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)imidazole-4-carboxamide ($\text{1b}$) through the carbonitrile ($\text{2b}$).     

Emission spectra of the noble-gas halides: the B12A12 system

The B$\text{1}\text{2}$—A$\text{1}\text{2}$ transition has been detected in the emission spectra of ArBr, KrBr, Krl and XeI at low pressure. Comparison with the well-known /ldB–X” continua implies that, in many cases, the latter is heavily overlapped by C$\text{3}\text{2}$—A$\text{3}\text{2}$ emission.     

Application of 2d-nmr spectroscopy in the structural determination of a new tobacco cembranoid

Proton-proton shift correlated 2D-NMR spectroscopy has been used to determine the structure of a new tobacco cembranoid as (1$\text{S}$,2$\text{E}$,4$\text{S}$,6$\text{R}$,7$\text{E}$)-4,6-dihy-droxy-2,7,12(20)-cembratrien-11-one (1). This assignment has been verified by chemical means.     

Calozeylanic acid,a new bark acid from three calophyllum species (guttiferae)

Calozeylanic acid has been isolated from the bark of three $\text{calophyllum}$ species: $\text{C.lankaensis}$ (= $\text{C.zeylanicum}$), $\text{C.thwaitesii}$ and $\text{C.walkeri}$. Its structure has been established as 2(R),3(R)-2,3-Dimetyl- 5-hydroxy-6-(3-methylbutanyl)-6-(3,7-dimethylocta-3,6-dienyl)-7-oxo-8- (2-carboxy-1-phenylethyl)-2,3,6,7-tetrahydrobenzo-4-pyrone.     

New tetrahydropyrans from a marine sponge

Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′$\text{R}$, 2$\text{S}$, 2″$\text{E}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′$\text{R}$, 2$\text{S}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran.     

Determination of the dipole moment of thioformaldehyde in the a3A2 excited state by laser phosphorescence excitation spectroscopy

Doppler-limited phosphorescence excitation spectra have been recorded at various electric fields for two rotational transitions in the $\text{a}$³A₂-$\text{X}$¹A₁ 0-0 band of H₂CS. Stark splittings were resolved, and were used to determine the dipole moment in the excited electronic state. The value found, 0.57(3) D, is of the order expected by comparison with dipole moments determined for other states of H₂CS, but rather lower than that predicted by ab initio calculations.     

Parviflorine,a glycosidic spirobenzylisoquinoline alkaloid

(+)-Parviflorine ($\text{1}$), found in $\text{Fumaria parviflora}$ Lam. (Fumariaceae), is the first known glycosidic spirobenzylisoquinoline alkaloid. Its acid hydrolysis yields (+)-parfumine ($\text{4}$) and D-glucose. Klyne's rule indicates that $\text{1}$ is a β-D-glucoside. The absolute configuration shown in expressions $\text{1-11}$ is predominant among spirobenzylisoquinolines. A generalization has been drawn between plant source and the oxygenation pattern of ring C for the spirobenzylisoquinoline alkaloids.     

A new stereocontrolled synthesis of d-ring aromatic steroid

D-Ring aromatic steroid (

having 19-methyl and C₆-nitro group has been stereo-selectively synthesised by an intramolecular cycloaddition of the $\text{o}$-quinodimethane ($\text{A}$) derived thermally from 5-acetoxy-2-[2-(1-cyano-4-methoxybenzocyclobutenyl)-1-nitroethyl]-1-ethenyl-1-methylcyclohexane (

).     

Rotational and vibrational temperatures of naphthalene in a naphthalene-argon supersonic jet

In the $\text{A}$¹B_2u-$\text{X}$¹A_g system of naphthalene in a supersonic jet, rotational contour calculations show rotational temperatures of 2–60 K for argon carrier gas pressures of 1520-120 Torr. The b_1u vibration v₂₄ shows a high vibrational temperature which corresponds to the seeding temperature for pressures <400 Torr.     

(4+2)-cycloaddition of nitroalkenes with ynamines; formation of a 4H-1,2-oxazine 2-oxide derivative

The formation of a thermally unstable (4+2)-cycloadduct, a 4H-1,2-oxazine 2-oxide derivative ($\text{1}$), from the reaction of 1-nitrocyclopentene with 1-phenyl-2-(1-pyrrolidinyl)acetylene has been proven by the structure elucidation of isoxazole derivative $\text{3}$ which results from thermal rearrangement and by the structure determination of the 1,3-dipolar adducts $\text{5}$ of $\text{1}$ with electron-deficient acetylenes.     

The ring closure and rearrangement of 1-(2-amino)-benzoyl-1-methylhydrazones of β-dicarbonyl compounds: on the formation and crystal structure of 3a,9a-dihydro- -1,3,3a,9a-tetramethyl-4H-pyrazolo[3,4-b]quinolin-4-one

The conversion of 1-(2-amino)-benzoyl-1-methylhydrazones of β-dicarbonyl compounds into heterocyclic derivatives yielded in addition to the already known type of product $\text{2}$ further three novel pyrazole derivatives $\text{3}$, $\text{4}$ and $\text{5}$. The structures of these products have been established by chemical and spectroscopic (MS) methods. The crystal structure of $\text{5}$ has been determined by X-ray diffraction.     

Cinncassiol D1 and its glucoside,novel pentacyclic diterpenes from cinnamomi cortex

A new pentacyclic diterpene with a new skeleton and its glucoside were obtained from the fraction exhibiting anti-complement activity of the water extractive of Cinnamomi Cortex. Their structures were elucidated as $\text{1}$ and $\text{3}$ by chemical, spectral and X-ray crystallographic studies.     

Large scale synthesis and absolute configuration of (-)-3-ppp,a selective dopamine autoreceptor agonist

A large scale synthesis for (-)-3-PPP has been developed. The racemic methoxy compound $\text{1}$ was prepared in a three step procedure in 63% yield. This was resolved as a diastereomeric salt by crystallization of the (-)-di-p-toluoyltartrate. Two crystallizations gave the pure (-)-enantiomer $\text{2}$ in 50% of the theoretical yield and with an enantiomeric excess of >95%. Demethylation using aqueous HBr gave (-)-3-PPP, ($\text{3}$). Compound $\text{2}$ was also prepared in a stereoselective synthesis from $\text{S}$-(-)- N-propyl-2- chloromethylpyrrolidine $\text{4}$. By X-ray crystallography it was shown that (-)-3-PPP has the $\text{S}$-configuration at the chiral carbon.     

Studies on the syntheses of heterocyclic and natural compounds. Part 939: An efficient and stereoselective synthesis of des-a-ring steroids—potential intermediates to estradiol,cortisone and progesterone

A stereoselective synthesis of des-A-ring steroids $\text{9}$ and $\text{17}$ has been achieved by an intramolecular cycloaddition of 3-isopropenyl-5-(4-methoxybenzocyclobutenyl) pentan-2-one-2-ethylene ketal $\text{7}$ and 1-(4-methoxy-benzocyclobutenyl)-4-methylpent-4-en-3-ol $\text{16}$, respectively.