0000000000178353
AUTHOR
Fiorenza Viani
Chiroptical Phenomena in Reverse Micelles: The Case of (1R,2S)-Dodecyl (2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium Bromide (DMEB)
(1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) aggregates dispersed in carbon tetrachloride have been investigated by Fourier transform infrared (FT-IR), vibrational circular dichroism (VCD) and 1H nuclear magnetic resonance (NMR) spectroscopy at various surfactant concentration and water-to-surfactant molar ratio. Experimental data indicate that, even at the lowest investigated concentration and in absence of added water, DMEB molecules associate in supramolecular assemblies. At higher DMEB concentration the aggregates can confine water molecules, making it plausible to think that DMEB form reverse micelles and that water molecules are quite uniformly dist…
Synthesis of nonracemic α-trifluoromethyl α-amino acids from sulfinimines of trifluoropyruvate
We describe a novel and useful method for the synthesis of nonracemic α-trifluoromethyl α-amino acids (α-Tfm-AAs). Key building blocks are the sulfinimines (S)-1a and (S)-1b, prepared by Staudinger reaction from trifluoropyruvate esters and the chiral N-sulfinyl iminophosphorane (S)-8, which were treated with benzyl, allyl, and alkylmagnesium halides. The resulting diastereomeric N-sulfinyl α-Tfm α-amino esters, 12 and 13, were produced with moderate to good stereoselectivity and yields. When alkyl Grignard reagents were used, stereocontrol became progressively higher with increasing steric bulk, while reversed, though poor, stereocontrol was achieved with benzyl/allyl Grignard reagents. An…