Vibrational frequencies and structural determinations of divinyl sulfoxide

We present a detailed analysis of the structure and infrared spectra of divinyl sulfoxide. The vibrational frequencies of the divinyl sulfoxide molecule were analyzed using standard quantum chemical techniques. Frequencies were calculated at the MP2 and DFT levels of theory using the standard 6-311G* basis set. The molecule exists normally in a C(s) configuration. High-energy forms of divinyl sulfoxide with C(S) and C(1) symmetries also exist.     

A weight-function approach for determining watershed initial conditions for combustion waves

In many generic combustion models, one finds that a combustionwave will develop with a specific wave speed. However, thereare possible initial temperature profiles which do not evolveinto such waves, but rather die out to the ambient temperature.There can exist, in some models, a clear distinction betweenthose initial conditions that do evolve into combustion wavesand those that do not; this is sometimes referred to as thewatershed initial condition. When fuel consumption is consideredto be negligible, analytical methods can be used to obtain theexact watershed. In this paper, we consider the problem of determiningpseudo-watersheds and ascertaining the relationship betweenthese pseudo-watersheds and the exact watersheds. In the processa novel weight-function approach for infinite spatial domainsis developed.     

A simple and highly effective oxidative chlorination protocol for the preparation of arenesulfonyl chlorides

2,4-Dichloro-5,5-dimethylhydantoin (DCDMH) was found to be a mild and efficient reagent for the direct oxidative conversion of sulfur compounds to the corresponding arenesulfonyl chlorides in good to excellent yields through oxidative chlorination. The method is suitable for many types of sulfur substrates (thiols, disulfides, and benzylic sulfides). The overall process is simple, practical, and it provides convenient access to a variety of aryl or heteroarylsulfonyl chlorides. The mild reaction conditions and the broad substrate scope render this method attractive and complementary to existing syntheses of aryl or heteroarylsulfonyl chlorides.     

Synthesis of cytotoxic cyanobactin,Wewakazole B

We report herein the synthesis of cytotoxic cyanobactin, Wewakazole B through an efficient solution-phase approach. The key steps of the synthesis are the macrocyclic lactamization of linear dodecapeptide and construction of two hexapeptides with three different substituted oxazole rings.     

An unusual intramolecular hetero-Diels-Alder cycloaddition

A new reaction of erythronolides, an intramolecular hetero-Diels-Alder, has been discovered. Heated aqueous alcoholic solutions of ABT-773 (1) and its cis isomer (3) convert slowly to cycloadducts 2 and 4, respectively. Optimal reaction conditions, mechanistic studies supported by molecular modeling, and biological activity data are reported. Single-crystal X-ray structures for both adducts 2 and 4 have been obtained.     

Bacterial mixture identification using Raman and surface‐enhanced Raman chemical imaging

The ability of normal Raman and surface‐enhanced Raman scattering (SERS) to identify and detect bacteria has shown great success in recent studies. The addition of silver nanoparticles to bacterial samples not only results in an enhanced Raman signal, but it also suppresses the native fluorescence associated with biological material. In this report, Raman chemical imaging (RCI) was used to analyze individual bacteria and complex mixtures of spores and vegetative cells. RCI uses every pixel or a binned pixel group (BPG) of the Raman camera as an independent Raman spectrograph, allowing collection of spatially resolved Raman spectra. The advantage of this technique resides primarily in the analysis of samples in complex backgrounds without the need for physically isolating or purifying the sample. Using a chemical imaging Raman microscope, we compare normal RCI to SERS‐assisted chemical imaging of mixtures of bacteria. In both cases, we are able to differentiate single bacterium in the Raman microscope's field of view, with a 60‐fold reduction in image acquisition time and a factor of 10 increase in the signal‐to‐noise ratio for SERS chemical imaging over normal RCI. Copyright © 2010 John Wiley & Sons, Ltd.