Richard M. Wing

Vitamin D in Solution: Conformations of Vitamin D3, α,25-Dihydroxyvitamin D3, and Dihydrotachysterol3

Solution conformations of the A and seco B rings of vitamin D3, 1α, 25-dihydroxyvitamin D3, 1α-hydroxyvitamin D3, and dihydrotachysterol3 have been established by high resolution, 300-megahertz proton magnetic resonance spectroscopy. The A ring of these steroids is dynamically equilibrated between two chair conformers. For vitamin D3, 1α-hydroxyvitamin D3, and 1α,25-dihydroxyvitamin D3 the relative proportions of the two conformers are 1 : 1, whereas dihydrotachysterol3 exists principally as only one conformer. Thus, the substituent groups on the A ring may be either equatorially or axially oriented, and suggests a refinement of the existing topological model for vitamin D hormonal activity.

Marine natural products-XVI: Polyhalogenated acyclic monoterpenes from the red alga plocamium of antarctica

Abstract Examination of the red alga Plocamium sp. collected near the Antarctic penninsula yielded three new acyclic halogenated monoterpenes ( 1 – 3 ). A structure revision is proposed for a compound previously reported to have structure 1 . X-ray diffraction provided the structure of 1 including absolute stereochemistry. The structures of 2 and 3 followed from proton and 13 C NMR spectral interpretation.

Melleolide, a new antibiotic from

Abstract Melleolide, a new sesquiterpenoid orsellinate, has been isolated from cultures of Armillaria mellea . Its structures was elucidated by X-ray crystallography.

Vibrational spectra and bonding in metal carbonyls VI. Evidence for a π-interaction between manganese pentacarbonyl and the perfluoromethyl group

Abstract The infrared spectrum of CF 3 Mn(CO) 5 has been investigated in the gas phase. The CF stretching bands are found at 1045 and 1063 cm p−1 and the shapes of the band envelopes indicate that these are the frequencies of the e and a 1 modes, respectively. Using these and other data, a calculation of the CF force constants in CF 3 Mn(CO) 3 and CF 3 I was made, the results (in md./A) being 4.6 and 5.9 respectively. This very substantial reduction in CF 3 Mn(CO) 5 is attributed to CF bond weakening by overlap of filled metal d π orbitals with CF σ antibonding orbitals.

The structure of the nickel bis(1,2-ethenedithiolate)/2,3-dimethylbutadiene cycloaddition reaction product

Summary The synthesis and chemistry of the cycloaddition products formed by reaction of various dienes with nickel bis(1,2-ethenedithiolate) is reported An orbital correlation model previously proposed in describing these and the related olefin reactions is supported by an X-ray diffraction study of the 2,3-dimethylbutadiene/nickel bis(1,2-ethenedithiolate) structure. This study confirms that the products formed by olefins and dienes are close structural relatives. Briefly the structures show a tetradentate sulfur ligand coordinated to square planar nickel. The central ring of the three chelate ring structure is formed in the cycloaddition reaction, and in the present case of a seven membered ring is completely strain free. Bond lengths and molecular properties suggest that reaction is redox in nature with nickel bis(1,2-ethenedithiolate) being the oxidant or acceptor molecule. The crystals studied were monoclinic P 2 1 / c with a =7.393(9), b =13.624(21), c = 20.003(26)A and β=90.80(5)°. The unit cell contains 4 formula units and the structure was solved using 1333 diffractometer measured intensities and refined to a final R factor of 0.094 based on F .

Chemical synthesis and biological activity of 3-deoxy-1α-hydroxyvitamin D3 an analog of 1α,25-(OH)2-D3, the active form of vitamin D3

The chemical synthesis of 3-deoxy-1α-hydroxyvitamin D3 from cholesterol is described. This steroid is a highly important analog of the hormonally active form of vitamin D, 1α, 25-dihydroxyvitamin D3; it is the only analog presently available for structure-function studies which lacks the 3β-hydroxyl but retains the key 1α-hydroxyl of 1α, 25-dihydroxyvitamin D3. The new steroid is highly biologically active; it stimulated intestinal calcium absorption significantly more rapidly than vitamin D3 and as rapidly as 1α, 25-dihydroxyvitamin D3.

Zonarene, a sesquiterpene from the brown seaweed Dictyopteris zonarioides☆

The major hydrocarbon component of the brown seaweed Dictyopteris zonarioides, zonarene, has been isolated and identified as the first C15H24 conjugated diene sesquiterpene of the cadanane type.

A Standard Session Stopped-Flow NMR Tube

An NMR tube has been designed to allow stopped-flow NMR experiments to be done with no modification of the instrument. Thus this technique is made routine for organic and inorganic chemists. The tube can be used with any iron magnet or super-conducting system, but the technique requires a Fourier transform data collection capability. The tube is easily attached to standard stopped-flow supply and stopping syringes, making routine data collection possible at a 0.6 s/spectra sampling rate. A calibration procedure and a sample chemical kinetic study are included to demonstrate the use of the tube.

Isocaespitol, a new halogenated sesquiterpene from Laurencia caespitosa

Abstract The halogenated sesquiterpene isocaespitol ( 1 ) has been isolated from the marine alga Laurencia caespitosa Lamx and its structure determined by X-ray crystallography.

Structure-function studies of the interaction of the hormonally active form of vitamin D3, 1α,25-dihydroxy-vitamin D3, with the intestine

Abstract The steroid cholecalciferol or vitamin D 3 is known to undergo a successive two-step hydroxylation, first in the liver to give 25-OH-D 3 and then in the kidney to produce 1α,25-(OH) 2 -D 3 . The kidney is postulated to be the endocrine gland which produces the biologically active form of vitamin D. The biological response to 1α,25-(OH) 2 -D 3 in the target intestine is believed to occur as a consequence of association with cytoplasmic and nuclear receptors, as is the case for other classical steroid hormones. A steroid competition assay has been devised using receptors present in the intestinal chromatin. A comparison of the relative competition in the assay and biological activity of a variety of analogs has defined some of the essential structural elements required for vitamin D activity. These structure-function relationships of analogs of 1α,25-(OH) 2 -D 3 are also discussed with particular emphasis on the A-ring conformation. It is emphasized that the A-ring of these seco-steroids consist of a pair of rapidly equilibrating chair conformers. As a consequence, different chair conformations produce different orientations of substituent groups in the A-ring. It is proposed that the 1α-hydroxyl of 1α,25-dihydroxyvitamin D 3 or its geometric equivalent in analogs must occupy the equatorial as opposed to the axial orientation for optimization of biological activity.