The convenient preparation of chiral tetrahydrothiophenes (THTs) in high enantiopurity via phosphorothioic acids and related compounds is reported. We consider these to be safer alternatives to the use of H(2)S which is a highly toxic gas. Each of the THTs is derived from a common intermediate, thereby greatly enhancing the flexibility of the synthesis. The key transformation is a base-promoted, intramolecular, carbon-sulfur bond-forming event. These reactions are highly stereospecific as they operate through a double S(N)2 displacement mechanism. The methodology is amenable to a broad array of functional groups and heterocycles. The tetrahydrothiophene motif is important because it is present in a number of bioactive natural products. They have also been utilized to promote various asymmetric transformations including hydrogenation, epoxidation, cyclopropanation, and aziridination reactions.
The synthesis of allylic thioethers arising from the reaction between phosphorothioate esters and alcohols is described. The synthesis is accomplished in one step by the addition of an exogenous alkoxide to the corresponding allylic phosphorothioate ester. It is demonstrated that this process is amenable to various functional groups and a wide variety of heterocycles. In contrast to conventional methods for thioether synthesis, no malodorous sulfur compounds such as thioacetic acid or thiols are required.
The development of an enzyme-mediated
reaction for the first-year
general, organic, and biological chemistry (GOB) teaching laboratory
is of significant importance so that the factors that affect enzyme-mediated
reactions can be adequately demonstrated, reinforcing the lecture
portion of the GOB course. Some of the factors that affect these types
of reactions include, but are not limited to, enzyme concentration,
substrate concentration, and temperature. The experiment reported
herein utilizes porcine pancreatic lipase (PPL) to catalyze the hydrolysis
of triglycerides within cream. The amount of time required to afford
triglyceride hydrolysis was probed by altering the concentration of
PPL and the temperature at which the reaction was performed. In addition,
to provide the students with a hands-on demonstration of how bile
salts aid in the digestion of triglycerides, various trials were performed
to explore the effect of altering bile salt concentration. Finally,
the data obtained from the enzyme concentration trials, the temperature
trials, and the bile salt concentration trials were graphed to provide
a visual representation of how triglyceride hydrolysis, mediated by
PPL, is affected by these various factors.
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