Enantiopure DAVA-derivatives-part III. Synthesis of all 4 stereoisomers of 2-methyl-4-hydroxy-5-aminopentanoic acid (2-Me-4-OH-DAVA).
摘要:
A stereoselective synthesis of the 4 stereoisomers of 2-methyl-4-hydroxy-5-amino-pentanoic acid namely 2R,4S-9a, 2S,4S-9b, ent-9a and ent-9b is presented, starting from the known lactones S-1 and R-l, which are readily available from L- and D-glutamic acid. Only ent-9b shows affinity for GABA(B)-receptor sites.
Bisaminal cyclization in the zoanthamine alkaloid system was strongly affected by the stereochemistry of the C4 methyl. While cyclization of the (4S)-methyl precursor gave only a bisaminal compound, cyclization of the (4R)-methyl isomer produced both spiroketal and bisaminal products.