Michael J. Girgis

Using mixed anhydrides from amino acids and isobutyl chloroformate in N-acylations: a case study on the elucidation of mechanism of urethane formation and starting amino acid liberation using carbon dioxide as the probe

Abstract A case study on the elucidation of mechanism of urethane by-product formation and starting amino acid liberation during the conventional two-step isobutyl chloroformate mediated N-acylation is described using carbon dioxide offgas as the probe. The main reason for the urethane formation and starting amino acid liberation was found to be the formation of the symmetrical anhydride of the amino acid during the preparation of the mixed carboxylic–carbonic anhydride intermediate, as determined by quantifying the evolved carbon dioxide. New conditions were developed to minimize this side reaction.

Feasibility of using gravimetry to measure excess adsorption effects of a binary solvent system in a reversed-phase high-performance liquid chromatography column

A modified method for weighing HPLC columns filled with solvent is described. The method prevents the loss of traces of solvent from within the threads of the column. The method was tested by obtaining the weights of a C18 column filled with 10 different organic solvents, showing a standard deviation on the order of 0.1%. A plot of gross column weight versus solvent density showed excellent linearity. The method was then used to weigh a column filled with several acetonitrile-water mixtures. The gross column weights were lower than would have been predicted from the density of the acetonitrile-water mixtures. A likely explanation is the existence of an adsorbed acetonitrile-rich liquid on the surface of the C18 adsorbent, which caused the lower than expected weights due to the lower density of pure acetonitrile relative to the bulk mixtures. The volume of pure acetonitrile required for the observed weight discrepancy was calculated. Based on the surface area of the column adsorbent, values of micromoles acetonitrile per square meter of surface area were determined. The values showed reasonable agreement with values obtained from published adsorption isotherm studies. This suggests that pycnometry may be a useful technique for adsorption studies. The limitations of the technique are discussed.

Optimization and Scale-Up of a Novel Process for 2-Aminoindan Hydrochloride Production

The need for an economical process for producing 2-aminoindan hydrochloride, a key starting material in manufacturing novel bioactive molecules, motivated development of a novel synthetic route using an inexpensive reactant, ninhydrin. The synthesis, involving oximation of ninhydrin followed by catalytic reduction of the resulting oxime intermediate to give 2-aminoindan, was demonstrated successfully, and a product purification scheme was developed to isolate 2-aminoindan as the hydrochloride salt form. Subsequent process development optimized the reduction step by identifying regimes of fast and slow reaction (corresponding to reduction of oxime and diketone functions, respectively), and tailoring reaction conditions to use mild conditions during the fast exothermic regime to ensure process safety followed by more severe conditions for the slower reaction. The process was successfully scaled up 100-fold in a pilot plant, with excellent yield and product quality agreement between laboratory and pilot plant.