Cyclopeptide and method for preparing the same

A method for preparing a cyclopeptide, comprising the following steps:

• (a) providing compounds represented by the following formulas (I-1) and (I-4):
• wherein, Ra, Rb and Re are each independently a protection group;
• Rc and Rd are each independently alkyl, cycloalkyl, aryl or heteroaryl;
• G is H or O-t-Bu;
• and
• R1 is
• in which R2 and R3 are each independently H or C1-6 alkyl;
• X is O, S, CH2, or N—R4, in which R4 is H, C1-6 alkyl, (CH2CH2O)nH, —C(═O)—C1-15 alkyl, —C(═O)CH2(OC2H4)nOR′ or C(═O)(C2H4)2C(═O)O(C2H4O)nR′, in which n=1-3 and R′ is H or CH3;
• (b) performing a reaction between the compounds of formulas (I-1) and (I-4) to obtain a compound represented by the following formula (I-5):
• (c) performing a reaction between the compound of formula (I-5) and the compound represented by the following formula (I-6) to obtain a compound represented by the following formula (I-7):
• wherein Rf is alkyl, cycloalkyl, aryl, or heteroaryl;
• and
• (d) performing a cyclization reaction of the compound of formula (I-7) with a catalyst of formula (II) and deprotection to obtain a compound represented by the following formula (III):
• M(O)mL1yL2z (II)
• wherein G′ is H or OH;
• Q is halogen, OC(O)CF3, or OC(O)CH3;
• M is a metal selected from the group consisting of IVB, VB, VIB and actinide groups;
• L1 and L2 respectively is a ligand;
• m and y are integers greater than or equal to 1;
• and
• z is an integer greater than or equal to 0.