Enantioselective synthesis of hydroxy-substituted ?-methyl-?-amino acids using Al and Mn derivatives of cyclo-(L-Ala-L-AIa) bis-Iactim ethers
摘要:
Aluminum and manganese derivatives of lithiated bis-lactim ethers of cyclo-(L-Ala-L-Ala) were used for the enantioselective synthesis of beta-hydroxy and polyhydroxy alpha-amino acids of the 2-methylserine series. A new variant of the synthesis of these acids via 3-acyl-2,5-dialkoxy-3,6-dimethyl-3,6-dihydropyrazines is proposed.
synthetic strategy based on a combination of sugar electrophiles and transition metal nucleophiles allows the metal carbenefunctionalization of acyclic carbohydrates. Following this methodology the per-O-acetylated methoxycarbene complexes 8–14 are prepared in moderate to good yields. Upon reaction with ammonia they undergo aminolysis to give the aminocarbene complexes 16–18. 1H-NMR studies indicate that in