the only way to give the macrodiolide in good yield [147] (Scheme 66). By contrast,
Corey–Nicolaou
[100],
Gerlach
[107],
Mukaiyama
[117],
and
Yamaguchi–Yonemitsu [135] procedures yielded no lactone, whereas the “regular”
Yamaguchi [89] protocol resulted in complete epimerization of the C2 stereogenic
center [147, 148].
Scheme 65 EDC-modified Boden–Keck protocol in the total synthesis of (+)-halichlorine, 229
Scheme 66 The DCC/pyridine/PPTS protocol in the synthesis of pamamycin-607, 232
Synthesis of 12- to 16-Membered-Ring Lactones
419