Onset of Mechanochromic Response in the High Strain Rate Uniaxial Compression of Spiropyran Embedded Silicone Elastomers.

The molecular processes that accompany dynamic mechanical response to large deformations at high strain rate (≈1000 s-1 or higher) underlie the early stages of damage in materials, but understanding of material response in this regime is typically limited to macroscopic constitutive equations. Here, spiropyran mechanophores are embedded in very short, stress-bearing strands in silicone elastomers, and their mechanochromic response to uniaxial compression is explored in a Split Hopkinson Pressure (or Kolsky) Bar. At strain rates of 1000 s-1 , the onset of mechanochromism occurs at lower strains, but higher stresses, than in the same materials under quasi-static loading. Similar to quasi-static loading, however, a negligible effect of mechanophore structure on the critical strain for colorimetric onset is observed. The results suggest that nonequilibrium, inhomogeneous local tension distributions in the elastomers lead to greater stress in individual strands than at the same strains under equilibrium loading, but that within the regions of force concentration, mechanochromic onset is determined primarily by a limiting local strain threshold.

D-Amino acid oxidase inhibitors based on the 5-hydroxy-1,2,4-triazin-6(1H)-one scaffold.

A series of 3-substituted 5-hydroxy-1,2,4-triazin-6(1H)-one derivatives were designed and synthesized as a new class of d-amino acid oxidase (DAAO) inhibitors. Some of the newly synthesized derivatives showed potent inhibitory activity against human DAAO with IC50 values in the nanomolar range. Among them, 6-hydroxy-3-phenethyl-1,2,4-triazin-5(2H)-one 6b and 3-((6-fluoronaphthalen-2-yl)methylthio)-6-hydroxy-1,2,4-triazin-5(2H)-one 6m were found to be metabolically stable in mouse liver microsomes. In addition, compound 6b was found to be orally available in mice and able to enhance plasma d-serine levels following its co-administration with d-serine compared to the oral administration of d-serine alone.

Construction of the tricyclic A-B-C core of the Veratrum alkaloids.

Organocatalyzed enantioselective allylation of 2-iodocyclohexenone followed by methylation and oxy-Cope rearrangement delivered enantiomerically enriched 2-methyl 3-allyl cyclohexanone, which engaged in acid-catalyzed Robinson annulation to give the bicyclic enone. Subsequent elaboration of the pendant allyl group into an α-diazo ß-keto ester set the stage for Rh-mediated cyclization to deliver the tricyclic A-B-C core of the Veratrum alkaloids.

Synthesis of kojic acid derivatives as secondary binding site probes of D-amino acid oxidase.

A series of kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) derivatives were synthesized and tested for their ability to inhibit D-amino acid oxidase (DAAO). Various substituents were incorporated into kojic acid at its 2-hydroxymethyl group. These analogs serve as useful molecular probes to explore the secondary binding site, which can be exploited in designing more potent DAAO inhibitors.

Enantioselective conjugate allylation of cyclic enones.

Enantioselective organocatalytic 1,2-allylation of a cyclic enone followed by anionic oxy-Cope rearrangement delivered the ketone as a mixture of diastereomers. This appears to be a general method for the net enantioselective conjugate allylation of cyclic enones.

The discovery and structure-activity relationships of indole-based inhibitors of glutamate carboxypeptidase II.

A series of N-substituted 3-(2-mercaptoethyl)-1H-indole-2-carboxylic acids were synthesized as inhibitors of glutamate carboxypeptidase II (GCPII). Those containing carboxybenzyl or carboxyphenyl groups at the N-position exhibited potent inhibitory activity against GCPII. These indole-based compounds represent the first example of achiral GCPII inhibitors and demonstrate greater tolerance of the GCPII active site for ligands with significant structural difference from the endogenous substrate, N-acetyl-aspartylglutamate.

Convenient synthetic route to an enantiomerically pure FMOC alpha-amino acid.

A strategy for the facile alpha-amination of carboxylic acid menthyl esters is described. The resulting diastereomers, readily separable, can be individually carried on to each enantiomer of the FMOC alpha-amino acid. A variety of unnatural side chains were compatible with this approach. The menthyl ester was easily removed from the FMOC alpha-amino acid without racemization.

Sexual size dimorphism and sexual selection in turtles (order testudines).

This paper combines published and original data on sexual size dimorphism, reproductive behavior, and habitat types in turtles. Our major finding is that observed patterns of sexual size dimorphism correlate with habitat type and male mating strategy. (1) In most terrestrial species, males engage in combat with each other. Males typically grow larger than females. (2) In semiaquatic and "bottom-walking" aquatic species, male combat is less common, but males often forcibly inseminate females. As in terrestrial species, males are usually larger than females. (3) In truly aquatic species, male combat and forcible insemination are rare. Instead, males utilize elaborate precoital displays, and female choice is highly important. Males are usually smaller than females.We interpret these correlations between sexual behavior and size dimorphism in terms of sexual selection theory: males are larger than females when large male size evolves as an adaptation to increase success in male combat, or to enable forcible insemination of females. In contrast, males are usually smaller than females where small size in males evolves to increase mobility (and hence, ability to locate females), or because selection for increased fecundity may result in increased female size. In turtle species with male combat or forcible insemination, the degree of male size superiority increases with mean species body size.

Synthesis and SAR of 1-hydroxy-1H-benzo[d]imidazol-2(3H)-ones as Inhibitors of D-Amino Acid Oxidase.

A series of 1-hydroxy-1H-benzo[d]imidazol-2(3H)-ones were synthesized and evaluated for their ability to inhibit human and porcine forms of D-amino acid oxidase (DAAO). Inhibitory potency is largely dependent on the size and position of substituents on the benzene ring with IC(50) values of the compounds ranging from 70 nM to greater than 100 µM. Structure-activity relationships of this new class of DAAO inhibitors will be presented in detail along with comparisons to previously published SAR data from other classes of DAAO inhibitors. Some of these compounds were given to mice orally together with D-serine to assess their effects on plasma D-serine pharmacokinetics.

Preparation of 2-iodo allylic alcohols from 2-butyn-1,4-diol.

The conversion of 2-butyn-1,4-diol to (Z)-2,4-diiodobut-2-en-1-ol proceeded efficiently using in situ generated trimethylsilyl iodide. Coupling with Grignard reagents and other nucleophiles delivered (2Z)-2-iodo allylic alcohols. The geometry of the products was established by nOe.