Synthesis of (R)- and (S)-3,3,3-trifluoro-2-phenylpropanoyl isocyanates and their use as reactive analogues of Mosher's acid

• Published in: Chirality (New York, N.Y.) Vol. 17; no. 7; pp. 378 - 387
• Main Authors: Vodička, Petr, Streinz, Ludvík, Vávra, Jan, Koutek, Bohumír, Buděšínský, Miloš, Ondráček, Jan, Císařrová, Ivana
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 2005
• Subjects: acyl isocyanate; auxiliary agent; chiral analysis; diastereomers; NMR
• ISSN: 0899-0042; 1520-636X
• DOI: 10.1002/chir.20176

The title compounds have been prepared from the respective 3,3,3‐trifluoro‐2‐methoxy‐2‐phenylpropanoic acids (MTPA) by a three‐step synthesis with MTPA chloride and MTPA amide as reaction intermediates. The requested compounds were obtained in high chemical yields without any change in optical purity during the preparation. To ascertain the usefulness of this auxiliary agent in the chiral analysis, isomeric 3,3,3‐trifluoro‐2‐phenylpropanoyl isocyanates were subjected in NMR tubes to noncatalyzed reactions with 16 different commercially available chiral alcohols. The steric arrangement of all diastereomers prepared correlated well with their NMR spectral nonequivalence data (Δδ), thus demonstrating the regular sign distribution of Δδ of particular groups according to the devised molecular model. The usefulness of the novel derivatization is discussed. Chirality 17:378–387, 2005. © 2005 Wiley‐Liss, Inc.