1999
E. Juaristi, M. Balderas, Heraclio López-Ruiz, V.M. Jiménez-Pérez, M. L. Kaiser-Carril y Y. Ramírez-Quirós. Enantioselective Synthesis of b-amino acids. Part 10: Preparation of novel a,a-and b,b-disubstituted b-amino acids from (S)-asparagine. Tetrahedron: Asymmetry, 10, 3493-3505 (1999). DOI: http://dx.doi.org/10.1016/S0957-4166(99)00328-6
Abstract
Perhydropyrimidinone (S)-1 is alkylated with very high diastereoselectivity to give trans products (2S,5R)-3, (2S,5R)4 and (2S,5R)-5. Dialkylation of (S)-1 also proceeds with complete stereoselectivity to afford adducts (2S,5R)-6, (2S,5S)-6, (2S,5R)-7 and (2S,5S)-7. Hydrolysis (6N HCl, 100C) of monoalkylated derivative (2S,5R)-3 gives enantiopure ?-substituted ?-amino acid (R)-8. Hydrolysis of dialkylated adducts 6 and 7 affords enantiopure ?,?-disubstituted ?-amino acids (R)- or (S)-9 and (R)- or (S)-10. Related iminoester (2S,6S)-2 is alkylated with complete diastereoselectivity to give products (2S,6S)-1113 whose hydrolysis under relatively mild conditions (2N CF3CO2H, CH3OH, 100C) affords enantiopure N-benzoylated ?,?-disubstituted ?-amino acid esters (S)-1416, with intact double bonds in the olefinic substituents.
Et3B, an Efficient Mediator for Xanthate Transfer Based Radical Processes
Study of the reactivity of squarylferrocenes. Addition of amines and aminoesters
Structural studies of spiroarsoranes derived from 2-aminophenols
Diastereoselective Synthesis of Spiro-?-lactams via Staudinger Reactio