| abstract |
The present invention provides a method for the purification of a 23-E isomer of a 23-imino derivative of a LL-F28249 compound having the structural formula I, wherein R is methyl, ethyl or isopropyl; R1 is H or methyl; and R2 has the meaning introduced in claims, reacts with the protecting agent and the base with producing the other mixture, containing the solid compound of general formula (II), wherein R, R1 and R2 have the meaning introduced with the general formula (I) and R3 is protecting group, second mixture is mixed with methanol and the compound of general formula (II) is separated and removed from the protecting group. |