Scheme 5.
Macrocyclization of 33 and x-ray structure of macroketolactone 35.a
a Reagents and conditions: (a) CSA, MeOH, 85%; (b) DMP, NaHCO3, 80%; (c) CrCl2, cat. NiCl2, DMSO, 50%; (d) DMP, Pyridine, 82%.
Macrocyclization of 33 and x-ray structure of macroketolactone 35.a
a Reagents and conditions: (a) CSA, MeOH, 85%; (b) DMP, NaHCO3, 80%; (c) CrCl2, cat. NiCl2, DMSO, 50%; (d) DMP, Pyridine, 82%.