Crystal and molecular structure of paclitaxel (taxol).

Paclitaxel (formerly called taxol), an important anticancer drug, inhibits cell replication by binding to and stabilizing microtubule polymers. As drug-receptor interactions are governed by the three-dimensional stereochemistries of both participants, we have determined the crystal structure of paclitaxel to identify its conformational preferences that may be related to biological activity. The monoclinic crystals contain two independent paclitaxel molecules in the asymmetric unit plus several water and dioxane solvent molecules. Taxane ring conformation is very similar in both paclitaxel molecules and is similar to the taxane ring conformation found in the crystal structure of the paclitaxel analogue docetaxel (formerly called taxotere). The two paclitaxel molecules have carbon-13 side-chain conformations that differ from each other and from that of the corresponding side chain in the docetaxel crystal structure. The carbon-13 side-chain conformation of one paclitaxel molecule is similar to what was proposed from NMR studies done in polar solvents, while that of the other paclitaxel molecule is different and hitherto unobserved. The paclitaxel molecules interact with each other and with solvent atoms through an extensive network of hydrogen bonds. Analysis of the hydrogen-bonding network together with structure-activity studies may suggest which atoms of paclitaxel are important for binding to microtubule receptors.

Solvent- and Ligand-free Diboration of Alkynes and Alkenes Catalyzed by Platinum Nanoparticles on Titania

Platinum nanoparticles supported on titania efficiently catalyzed the diboration of alkynes and alkenes under solvent- and ligand-free conditions in air. The cis-1,2-diborylalkenes and 1,2-diborylalkanes were obtained in moderate to excellent yields following, in most cases, a simple filtration workup protocol. The versatility of the cis-1,2-diboronvinyl compounds was demonstrated in a series of organic transformations, including the Suzuki–Miyaura cross coupling and the boron–halogen exchange.

Calculus for business and related fields,

Mode of access: Internet.

Seventh report on the oil and gas fields of western Pennsylvania. For 1887, 1888, with additional unpublished well records.

Mode of access: Internet.

Film bibliography of aviation and related fields.

Cover title.

Academic research equipment and equipment needs in selected science and engineering fields, 1989-90 /

Mode of access: Internet.

Michigan's oil and gas fields.

Vols. for 1964- issued as even numbered issues of its Annual statistical summary.

Investigations in the gas and oil fields of Alberta, Saskatchewan, and Manitoba,

Mode of access: Internet.

Michigan's oil and gas fields.

Mode of access: Internet.

Summary of operations, oil and gas fields.

Mode of access: Internet.

The secret of pictorial art, or, Self-instructor in painting on glass, china, satin and paper : it teaches the oil photo-miniature, Grecian oil, antique, oriental, crystal and pastel paintings, crystalline, decalcomanie and diaphanie transferring /

Includes index.

The Oil and gas fields of southeastern New Mexico : a symposium /

Cover title: A symposium of oil & gas fields of southeastern New Mexico, 1956.

The scientist as a person; report of a study of technically-trained personnel whose function is conducting research in chemistry and related fields of science in the Du Pont Company.

Errata slip inserted.

Historic mansions and highways around Boston. Being a new and rev. ed. of "Old landmarks and historic fields of Middlesex."

Mode of access: Internet.