Christopher G. Hamaker

Cuticular hydrocarbons as a basis for chemosensory self-referencing in crickets: a potentially universal mechanism facilitating polyandry in insects.

Females of many species obtain benefits by mating polyandrously, and often prefer novel males over previous mates. However, how do females recognise previous mates, particularly in the face of cognitive constraints? Female crickets appear to have evolved a simple but effective solution: females imbue males with their own cuticular hydrocarbons (CHCs) at mating and utilise chemosensory self-referencing to recognise recent mates. Female CHC profiles exhibited significant additive genetic variation, demonstrating that genetically unique chemical cues are available to support chemosensory self-referencing. CHC profiles of males became more similar to those of females after mating, indicating physical transfer of CHCs between individuals during copulation. Experimental perfuming of males with female CHCs resulted in a female aversion to males bearing chemical cues similar to their own. Chemosensory self-referencing, therefore, could be a widespread mechanism by which females increase the diversity of their mating partners.

Producing biodiesel using whole-cell biocatalysts in separate hydrolysis and methanolysis reactions.

This research examined the effect of using separate hydrolysis and methanolysis reactions for biodiesel production using a whole-cell biocatalysts derived from Rhizopus Oryzae (ATCC 10260). Biodiesel yield from separate hydrolysis and methanolysis was compared to transesterification reactions where both hydrolysis and methanolysis reactions occur in the same reactor. All reactions were conducted at room temperature. The effect of substituting ethanol for methanol was also studied. Separating the hydrolysis and methanolysis reactions did not significantly increase biodiesel yields; however, this approach successfully converted about 99% of triglycerides into fatty acid methyl esters (FAME) and free fatty acids (FFA). Use of ethanol in place of methanol did not significantly improve the biodiesel yield. However, there is evidence that ethanol may either esterify FFA more quickly than methanol, or result in a more stable ester. The best biodiesel yield was about 90% when a transesterification reaction using methanol was followed by one hydrolysis and one ethanolysis reaction; however, this is only slightly higher than the 88% biodiesel yield of two transesterification reactions in series (using methanol as alcohol).

Use of a whole-cell biocatalyst to produce biodiesel in a water-containing system

This study examined the use of a whole-cell biocatalyst to transesterify triglycerides, including high-Free Fatty Acid (FFA) waste greases, in a water-containing system. The whole-cell biocatalyst derived from Rhizopus oryzae (ATCC10260) was grown and reacted at room temperature without immobilization. The effectiveness of improving biodiesel yield through alteration of reaction temperature, additional alcohol, and additional transesterification reaction was also examined. Results showed that whole-cell biocatalyst was able to produce biodiesel with a yield of about 75% for virgin canola oil, 80% for waste vegetable oil and 55% for brown grease with a 72-hr transesterification reaction using no excess methanol. Elevating the reaction temperature to 35°C significantly diminished the yield. An additional dose of methanol with another 24 hours of reaction time or a second 72-hr reaction resulted in biodiesel yield approaching 90% and only 3% residual glycerides (mono-, di- and tri-glycerides). These results suggest that whole-cell biocatalysts are able to transesterify waste oils or greases that are high in FFA and contain water. Brown (trap) grease and similar degraded or complex greases may be good candidates for further whole-cell biocatalyst research.

Synthesis, X-Ray Crystallography, and Reactions of N-Acyl and N-Carbamoyl Succinimides

Abstract A collection of N-acyl and N-carbamoyl succinimides were prepared by acylation of succinimide with acyl chlorides or by ethylene dichloride (EDC) coupling of carboxylic acids. The x-ray crystal structures of N-benzoyl and N-p-nitrobenzoyl succinimides were determined. The N-acyl succinimides were effective in acylating primary amines, a secondary amine, and an aromatic amine. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

Unique Reactivity of anti- and syn-Acetoxypyranones en Route to Oxidopyrylium Intermediates Leading to a Cascade Process

Unique reactivity of anti- and syn-acetoxypyranones was observed in oxidopyrylium-alkene [5 + 2] cycloadditions. The subtle interplay between the corresponding acetoxypyranone conformation and steric bulk of tertiary amine bases causes syn-acetoxypyranones to undergo [5 + 2] cycloaddition appreciably faster than anti-acetoxypyranones. Additionally, the efficiency of a cascade process that afforded a novel tetracyclic lactol was determined to be dependent on the relative stereochemistry of each diastereomer, the amine base utilized, and the addition of water.

Oxidopyrylium-Alkene [5 + 2] Cycloaddition Conjugate Addition Cascade (C3) Sequences: Scope, Limitation, and Computational Investigations

Oxidopyrylium-alkene [5 + 2] cycloaddition conjugate addition cascade (C3) sequences are described. Intramolecular cycloadditions involving terminal alkenes, enals, and enones were investigated. Substrates with tethers of varying lengths delivered five- and six-membered carbocycles and heterocycles thus demonstrating the scope and limitation of the cycloaddition-conjugate addition cascade. Several experiments and theoretical calculations provide evidence for the proposed mechanistic pathway.

3,5-Di-tert-butyl-N-[2-(methyl­sulfan­yl)phen­yl]salicylaldimine

The molecule of the title compound, C22H29NOS, is non-planar, with a dihedral angle of 32.06 (9)° between the two aromatic rings.

N-(3,5-Dimethoxybenzylidene)-2-(methylsulfanyl)aniline

Schiff base ligands are versatile ligands due to their ease of synthesis and their ability to be readily modified electronically and sterically. Schiff base ligands have been used to model enzymes (Santra et al., 2002) and as supporting ligands in asymmetric catalysis (Xia et al., 2005). Our group is interested in the synthesis and coordination chemistry of mixed-donor Schiff base ligands containing sulfur donors (Hamaker & Corgliano, 2006; Hamaker & Halbach, 2006; Hamaker et al., 2006). As a part of our studies, we report the crystal structure of the title compound, (I).