Synthesis of (S)- and (R)-1-(2-furyl)alkylamines and (S)- and (R)-α-amino acids through the addition of organometallic reagents to imines derived from (S)-valinol

(S)-1-(2-Furyl)alkylamines were prepared through the addition of organometallic reagents to the imine derived from 2-furaldehyde and (S)-valinol, previous protection of the auxiliary hydroxy group as trimethylsilyl ether, followed by removal of the auxiliary. Then, protection of the primary amine as tosylamide or benzamide and oxidation of the furan ring gave the N-derivatives of (S)-alpha-amino acids. (R)-N-Benzoylphenylglycine was prepared from the benzaldimine, where the hydroxy group was protected as the tert-butyldimethylsilyl ether, through addition of 2-furyllithium.