Browsing by Author "Kunz, Horst"
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Item Open Access Carbohydrates as chiral templates : diastereoselective synthesis of N-glycosyl-N-homoallylamines and β-amino acids from imines(1991) Laschat, Sabine; Kunz, HorstComplexing properties and chirality of carbohydrates were utilized in diastereoselective reactions of 0-pivaloylated N-galactosylimines with allylsilanes and -stannaries. With dyltrimethylsilane in the presence of SnCl4, imines 2 of aromatic and heteroaromatic aldehydes were converted to homdylamines 3, giving ratios of diastereomers higher than 7:1. No addition products derived from α-anomeric aromatic imines were formed. Aliphatic homdylamines 3 were synthesized by using allyltributylstannane in the presence of SnCl4. Both α- and β-anomeric aliphatic imines reacted with the allylstannane. They gave the same ratio of diastereomers and showed the same sense of asymmetric induction.Item Open Access Carbohydrates as chiral templates : stereoselective synthesis of (R)- and (S)-α-aminophosphonic acid derivatives(1992) Laschat, Sabine; Kunz, HorstThe stereoselective synthesis of diethyl (S)- or (R)-α-[(O-pivaloyl-hexapyranosyl) amino]benzylphosphonates is achieved via Lewis acid catalyzed addition of diethyl phosphite to O-pivaloylated N-benzylidene -β-D-galactosylamine or N-benzylidene-α-D-arabinopyranosylamine. The process can also be performed by a one-pot procedure selectively giving (S)-aminophosphonic acid derivatives from galactosylamine and (R)-aminophosphonic acid derivatives from β-L-fucosylamine as the chiral auxiliaries.Item Open Access Carbohydrates as chiral templates : stereoselective synthesis of (R)-homoallyl amines using L-fucose as the auxiliary formally enantiomeric to D-galactose(1990) Laschat, Sabine; Kunz, Horst(R)-Homoallyl amines are synthesized with high asymmetric induction using the diastereoselective Lewis acid induced addition of allylsilanes and allylstannanes to Schiff bases of O-acyl protected fucopyranosylamine.Item Open Access Carbohydrates as chiral templates : stereoselective synthesis of chiral homoallyl amines and β-amino acids(1990) Laschat, Sabine; Kunz, HorstEnantiomerically pure homoallyl amines and β-amino acids are synthesized using the diastereoselective Lewis acid induced addition of allylsilanes and allylstannanes to Schiff bases of O-aryl protected galactopyranosylamine.Item Open Access Stereoselective synthesis of amino acid derivatives using carbohydrates as templates(1993) Kunz, Horst; Sager, Wilfried; Pfrengle, Waldemar; Laschat, Sabine; Schanzenbach, DirkGlycosylamines contain the easily cleavable semi-aminal-type N-glycosidic bond. O-Protected glycosylamines, therefore, can advantageously be used as a form of "asymmetric ammonia", for instance, in Strecker syntheses and in Ugi reactions to give amino acid amides as well as in modifications of the Mannich reaction.