(EN) Processes for the preparation of Cryptophycins of the formula (II), wherein G is (C1-C12) alkyl, (C2-C12) alkenyl, (C2-C12) alkynyl, or Ar; R1 is halogen and R2 is OH or glycinate ester; or R1 or R2 may be taken together to form an epoxide ring; or R1 or R2 may be taken together to form a bond; R3 is (C1-C6) alkyl; R7 and R8 are each independently hydrogen or (C1-C6) alkyl; or R7 and R8, may be taken together to form a cyclopropyl or cyclobutyl ring; R9 is hydrogen, (C1-C6) alkyl, (C2-C6) alkenyl, (C2-C6) alkynyl, -(CH2)m-(C3-C5)cycloalkyl or benzyl; R10, R14 is hydrogen or (C1-C6) alkyl; R11 is hydrogen, (C1-C6) alkyl, phenyl or benzyl; R50 is hydrogen or (=0); Y is CH, O, NR12, S, SO, SO2, wherein R12 is hydrogen or (C1-C3) alkyl; R6 is (C1-C6) alkyl, substituted (C1-C6)alkyl, (C3-C8)cycloalkyl, substituted (C3-C8)cycloalkyl, a heteroaromatic or substituted heteroaromatic group or a group of formula (IA), (IB) OR (IC). The processes involve an asymmetric crotylboration and, in the preferred embodiment, a subsequent asymmetric allylboration, providing for an efficient method for preparing Fragment A of the Cryptophycin molecule.
(FR) L'invention concerne des procédés permettant de préparer des dérivés de cryptophycine. Ces procédés consistent en une crotylboration asymétrique et, dans le mode de réalisation préféré, en une allylboration asymétrique consécutive, ce qui permet d'obtenir une méthode efficace de préparation du fragment A de la molécule de cryptophycine.