David N. Harpp

A simple method to prepare unsymmetrical di- tri- and tetrasulfides

Unsymmetrical di- tri- and tetrasulfides can be prepared in a one-pot reaction using SO2Cl2, SCl2 and S2Cl2 respectively to permit coupling of the appropriate thiols.

Stereoselection in the condensation between ethyl propionate and aldehydes

Abstract Ethyl propionate can be converted stereoselectively into geometrical isomers of O-ethyl-O-trimethylsilylmethylketene acetal ( 5 ). The E-isomer of 5 condenses with aldehydes by titanium tetrachloride to give stereoselectively the threo isomers of ethyl 2-methyl-3-hydroxy carboxylates.

Microbiota and Neurological Disorders: A Gut Feeling

Abstract In the past century, noncommunicable diseases have surpassed infectious diseases as the principal cause of sickness and death, worldwide. Trillions of commensal microbes live in and on our body, and constitute the human microbiome. The vast majority of these microorganisms are maternally derived and live in the gut, where they perform functions essential to our health and survival, including: digesting food, activating certain drugs, producing short-chain fatty acids (which help to modulate gene expression by inhibiting the deacetylation of histone proteins), generating anti-inflammatory substances, and playing a fundamental role in the induction, training, and function of our immune system. Among the many roles the microbiome ultimately plays, it mitigates against untoward effects from our exposure to the environment by forming a biotic shield between us and the outside world. The importance of physical activity coupled with a balanced and healthy diet in the maintenance of our well-being has been recognized since antiquity. However, it is only recently that characterization of the host–microbiome intermetabolic and crosstalk pathways has come to the forefront in studying therapeutic design. As reviewed in this report, synthetic biology shows potential in developing microorganisms for correcting pathogenic dysbiosis (gut microbiota–host maladaptation), although this has yet to be proven. However, the development and use of small molecule drugs have a long and successful history in the clinic, with small molecule histone deacetylase inhibitors representing one relevant example already approved to treat cancer and other disorders. Moreover, preclinical research suggests that epigenetic treatment of neurological conditions holds significant promise. With the mouth being an extension of the digestive tract, it presents a readily accessible diagnostic site for the early detection of potential unhealthy pathogens resident in the gut. Taken together, the data outlined herein provide an encouraging roadmap toward important new medicines and companion diagnostic platforms in a wide range of therapeutic indications.

Sulfur Extrusion Reactions - Scope and Mechanistic Aspects

Abstract This review details a significant and representative set of examples in the literature where one of the products in a chemical reaction is elemental sulfur. While the mechanism of such extrusions is not clearly understood, several mechanistic possibilities have been considered including the likelihood of thiosulfoxide intermediates, the concatenation of sulfur atoms and the elimination of singlet diatomic sulfur as a discrete species. Details of the mechanistic efforts that have been uncovered in the literature are included as well as our own work in this area. In order to help avoid confusion for the reader, the nomenclature (although sometimes inconsistent) is in most cases that which appeared in the original articles.

Bis(triphenylstanyl)telluride a mild and selective reagent for telluration and debromination

Abstract Bis(triphenylstannyl)telluride 1 coupled with fluoride ion is a mild telluration reagent in a reaction with dihalides. In addition, this combination constitutes a very effective debromination procedure for the high-yield formation of olefins from 1,2-dihalides.

Recent chemistry of the chalcogen diatomics

Abstract The chemistry of the generation and trapping of diatomic sulfur (S 2 ) and sulfur monoxide (SO) are reviewed with special emphasis on recent work, including initial efforts to detect and trap diatomic selenium (Se 2 ).

Cyano and fluorodestannylation: A new methodology using some powerful sulfur transfer reagents, the organotin sulfides☆

Abstract Fluoride and cyanide ions destannylate bis(aralkyl)tin sulfides [R3SnSSnR3] and trialkyltin sulfides [R3SnSR′ (R = alkyl)] giving, in the presence of a variety of alkyl and activated halides, the corresponding thioether derivatives in excellent yield. The conditions are mild, neutral and anhydrous; a strong solvent effect is noted. Special comments are made concerning work-up procedures.

Chemistry of a molybdenum-persulfide complex: Alkylation and oxidative coupling

Abstract The reaction of alkyl halides, sulfinyl and sulfonyl chlorides with (NH4)2[(S2)2MO(S2)2MO(S2)2] has been found to afford sulfides and disulfides in good-excellent isolated yield. The effect of solvent polarity and reaction time is discussed.

Insertion of a two sulfur unit into the S–S bond—tailor-made polysulfides

Abstract Triphenylthiosulfenyl chloride (1) reacts with disulfides RSSR, yielding tetrasulfides as the main products. The results of the insertion for different R groups are reported. A two-step mechanism involving the formation of unsymmetrical trisulfide intermediates containing the trityl group is proposed.

High yield preparation of cyclic disulfides using alkyltin thiolates

Abstract Cyclic disulfides with ring sizes ranging from 5 to 10 are formed by iodination or bromi nation of alkyltin thiolates without the need of high dilution.