The isolation and structure of 6″-bromo-isoarboreol - the first bromine containing lignan

A new lignan from $\text{Gmelina arborea}$ is shown to be 1, 2a-dihydroxy-2e-piperonyl-6e-(6″-bromopiperonyl)-3, 7-dioxabicyclo-[3,3,0]-octane, the first example of a bromine containing lignan.     

New lipids from the soft corals of the Andaman Islands

Sphingolipids and glycolipids including previously unknown (2S,3S,4R)-1,3,4-trihydroxy-2-(2-(R)-hydroxyoctadecanoylamino)octadec-8E-ene, (2S,3R)-1,3-dihydroxy-2-octadecanoylamino-4E,8E-hexadecadiene, and (2-hydroxy-3-hexadecyloxypropyl)--L-fucopyranoside were isolated from soft corals collected on the shelf near the Andaman Islands (Indian Ocean). The structures of all compounds were established by spectroscopic methods and chemical analyses. The lipids possessed antibacterial activity against Bacillus subtilis, Bacillus pumilus, Escherichia coli, and Pseudomonas aeruginosa and antifungal activity against Aspergillus niger, Rhizopus oryzae, and Candida albicans.     

Synthesis and Characterization of Related Compounds of Aripiprazole,an Antipsychotic Drug Substance

Three related compounds of aripiprazole were identified during the synthesis. These related compounds were synthesized and characterized by their respective spectral data.     

Synthesis of 10-Hydroxycamptothecin: Evaluation of New Moderators for the Chemoselective Reduction of Camptothecin

Abstract

10-Hydroxycamptothecin is prepared by chemoselective catalytic hydrogenation of the B-ring of camptothecin over PtO₂ with sulfur moderators followed by oxidation using iodobenzenediacetate. New moderators (viz. thioanisole, dimethyl sulfide, diphenyl sulfide, 2-mercapto ethanol), which moderate the hydrogenation of the B- ring of camptothecin, are being explored.

MOLECULAR PACKING IN TRIACYL-sn-GLYCEROLS: INFLUENCES OF ACYL CHAIN LENGTH AND UNSATURATION

The molecular packing in triacylglycerols having different acyl chains has been examined by differential scanning calorimetry, powder X-ray diffraction and vibrational spectroscopy (infrared and Raman) techniques. In the triacylglycerols examined, the acyl chain length, unsaturation or the position of substitution on the glycerol were changed systematically to observe their influence on the molecular packing in different polymorphic forms. Variation in the 3-acyl chain length of 1,2-dipalmitoyl-3-acyl-sn-glycerols (PPX) influenced the molecular packing along the long axis in the stable polymorphic forms. Three different modes of packing were observed. If X ≤ 4, the compounds packed in a bilayer structure similar to diacylglycerols, or if X ≥ 10 and ≤ 16 the compounds packed in a bilayer structure but similar to mono acid triacylglycerols. However for intermediate 3-acyl chain lengths, as in PP6 and PP8 the stable packing can occured only through chain segregation resulting in a trilayer structure. In the triacylglycerols containing unsaturated acyl chains, 1,2-dioleoyl-3-acyl-sn-glycerols (00X) and 1,3-dioleoyl-Z-acyl-sn-glycerols (0X0) the stable polymorphic forms packed in a trilayer structure where the odd acyl chains segregated and formed a middle layer. In a metastable hexagonal packing (α-phase) the long range ordering is minimal. Because of this lack of specific chain-chain interaction the 3-short acyl chain compounds of PPX packed in a unimolecular length structure (except PP2) whereas the 3-long acyl chain compounds packed in a bilayer structure. In orthorhombic perpendicular and triclinic parallel packing where the specific chain-chain interaction is increased, the end plane methyl packing and the glycerol conformation played important roles in the formation of bi-, tri- and hexalayer structures. The driving force in the formation of these different structures is to minimize the crystal defects created by the odd acyl chains and to enhance the specific chain-chain interactions. The presence of an odd acyl chain influenced the lateral chain packing as well, e.g., the stability of the orthorhombic perpendicular packing is enhanced by the presence of an odd acyl chain and even in some cases it is favored over the triclinic parallel packing. The odd acyl chain at the 1- or 3position of -sn-glycerol stabilized the orthorhombic perpendicular packing. This indicates the glycerol conformation is probably perpendicular to the layer plane and thus is different from the monoacid triacylglycerols.     

Synthesis of twist-twist pi-conjugated di-sec-alkylstilbenes and stilbene polymers

Twist-twist pi-conjugated (TTPC) pi systems promise unique properties with their 90 degrees twist angles. Di-sec-alkyl substituted stilbenes, 5, were prepared by low-valent titanium coupling of phenyl ketones, 4. Long alkyl chains stopped the coupling reaction. Stilbenes 5 were shown to be approximately 90% TTPC. Inserting TTPC units into poly(p-phenylene) polymers created highly fluorescent, soluble, TTPC pi systems with weak electronic segmentation for organic light emitting diode (OLED) studies.     

Alternative Synthesis and the Determination of Absolute Configuration of Docetaxel,an Anticancer Drug

Abstract

A simple, efficient, and alternative synthetic route for docetaxel with better control on the protection–deprotection sequence has been developed. The process is easily scalable and commercially viable, and critical impurities can be controlled efficiently. For the first time, absolute configuration of docetaxel was determined unambiguously by single-crystal x-ray diffraction.     

An Ethenoadenine FAD Analog Accelerates UV Dimer Repair by DNA Photolyase

Reduced anionic flavin adenine dinucleotide (FADH^?) is the critical cofactor in DNA photolyase (PL) for the repair of cyclobutane pyrimidine dimers (CPD) in UV‐damaged DNA. The initial step involves photoinduced electron transfer from *FADH^? to the CPD. The adenine (Ade) moiety is nearly stacked with the flavin ring, an unusual conformation compared to other FAD‐dependent proteins. The role of this proximity has not been unequivocally elucidated. Some studies suggest that Ade is a radical intermediate, but others conclude that Ade modulates the electron transfer rate constant (k_ET) through superexchange. No study has succeeded in removing or modifying this Ade to test these hypotheses. Here, FAD analogs containing either an ethano‐ or etheno‐bridged Ade between the AN1 and AN6 atoms (e‐FAD and ε‐FAD, respectively) were used to reconstitute apo‐PL, giving e‐PL and ε‐PL respectively. The reconstitution yield of e‐PL was very poor, suggesting that the hydrophobicity of the ethano group prevented its uptake, while ε‐PL showed 50% reconstitution yield. The substrate binding constants for ε‐PL and rPL were identical. ε‐PL showed a 15% higher steady‐state repair yield compared to FAD‐reconstituted photolyase (rPL). The acceleration of repair in ε‐PL is discussed in terms of an ε‐Ade radical intermediate vs superexchange mechanism.     

Existence of double-pinning force maxima for a single pinning mechanism

Critical current measurements on a cold rolled Pb₆₀In₄₀ foil show two pinning maxima, one close to H_c2 in the neighborhood of h = 0.95, and the other at low fields around h = 0.15. The high field pinning force maximum shifts to lower fields, and the low field maximum shifts to higher fields with increasing pinning strength. The data is explained in terms of Kramer's pinning force model incorporating Brandt's expression for C>₆₆.