Nakiterpiosin, a novel cytotoxic C-nor-D-homosteroid from the Okinawan sponge Terpios hoshinota

A novel cytotoxic compound, nakiterpiosin (1), was isolated from the Okinawan sponge Terpios hoshinota. Its structure was determined by spectroscopic analysis. The absolute stereostructure of 1 was also determined by a modified Mosher's method. Nakiterpiosin showed potent cytotoxicity against P388 cells.     

A new disaccharide,glaucobiose from Chinese drug “Pai-ch'ien”: A comparison of 13C NMR with its diastereomeric isomer,strophanthobiose

The structure of a new disaccharide named glaucobiose (4) has been established, and the ¹³C NMR of its methyl β- (5) and α-glycoside (6), and that of methyl β-strophanthobioside (2) were studied.     

Microwave spectrum, structure, dipole moment, and internal rotation of fluoromethyl methyl ether

Microwave spectra of fluoromethyl methyl ether and its 10 isotopically substituted species were measured. The r_s structure of this molecule was determined from the observed moments of inertia. Structural parameters obtained for this molecule, which was in the gauche form, were compared with those of the analogous molecules. Dipole moments of the normal and two deuterated species were determined by Stark-effect measurements. For the normal species, the dipole moment is 1.744 ± 0.029 D making an angle of 100°54′ with the O---CH₂ bond toward the C---F direction and lies in the plane whose dihedral angles with the FCO and COC planes are 114°9′ and 44°56′, respectively. The barrier to internal rotation of the methyl group was calculated taking into account the coupling effect with the skeletal torsion using the observed splitting data of the spectra in the ground, first excited methyl torsional, and skeletal torsional states. The barrier, skeletal torsional frequency, and coupling term were determined to be V₃ = 1538 ± 40 cal/mole, ω_t = 158 ± 4 cm⁻¹, and V_s = 490 ± 500 cal/mole, respectively.     

Use of ligand buffers for improved selectivity in the polarographic determination of metals Polarographic determination of zinc in the presence of a large amount of cadmium

The use of ligand buffers composed of a chelating agent and an excess of polarographically inert metal is recommended for the selective polarographic determination of a metal in the presence of a second metal, which has a polarographic wave at a less negative potential than the metal to be determined. Theoretical considerations on the optimum ligand concentration and the optimum composition of the ligand buffer are followed by the determination of zinc in cadmium as an example.     

Ultrasonic measurements of the elastic moduli of ultradrawn polyoxymethylene

We have employed an ultrasonic method to measure from ?40 to 60°C the five independent elastic moduli C₁₁, C₁₃, C₃₃, C₄₄, and C₆₆ of polyoxymethylene with draw ratio λ from 1 to 26 prepared by continuous drawing under microwave heating. The elastic moduli are controlled by three major factors: molecular orientation in the crystalline regions, fraction of noncrystalline taut tie molecules, and void content. The steep rise in the axial extensional modulus C₃₃ and axial Young's modulus E₀ with increasing draw ratio results from the alignment of chains in the crystalline blocks and an increase in the number of disordered taut tie molecules. Below the γ relaxation (located at 0°C at our measurement frequency of 10 MHz), these two factors also give rise to a slight decrease in the transverse extensional modulus C₁₁, Young's modulus E₉₀ and shear modulus C₆₆. At high temperature where the amorphous regions have very low modulus, the stiffening effect of taut tie molecules becomes dominant, leading to an increase in all moduli as λ increases from 1 to 10. At higher λ the void fraction increases appreciably, causing small decreases in E₉₀, C₁₁, and C₆₆ at all temperatures.     

Revised structure of diastereomeric 3,8-di-t-butylspiro[4,4]nonane-1,6-diones

The recently assigned diastereomeric configuration of 3,8-di-t-butylspiro[4.4]nonane-1,6-dione has been revised based on the X-ray analysis.