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The cyclic 16-membered pentadepsipeptide cyclo(Tro-Aib-Aib-Aib-Aib) (1) was crystallized from MeOH/ AcOEt/CH 2 Cl 2 , and its structure was established by X-ray crystallography (Fig. 1). There are two symmetryindependent molecules with different conformations in the asymmetric unit. Two intramolecular H-bonds stabilize two b-turns in each molecule. On the other hand, two of the four Aib residues are forced to assume a nonfavorable nonhelical conformation in each of the symmetry-independent molecules ( Table 1). The conformational study in CDCl 3 solution by NMR spectroscopy and molecular dynamics (MD) simulations indicate that the averaged structure (Fig. 3) is almost the same as in the solid state.

The methylcobalt compounds (III) are tested in the methylation of the bromostyrene (I) and various carbonyl compounds such as (II), (VII), or (IX).