in each case , the 7s adduct is the major product , with the observed stereoselectivities ( 7s to 7r ) ranging from 2.6 to 1 for n-acetyl-l-cysteine to 4 to 1 for both the n- ( tert-butoxycarbonyl ) -l-cysteine and 1-thio-beta-d-glucose as nucleophiles .
C0001047
n-acetyl-l-cysteine
C0010654
l-cysteine