10.3 14-Membered Macrocyclic Lactones
10.3.1 Narbonolide
The intramolecular NHK coupling reaction was also used to complete the total
synthesis of narbonolide 138, a 14-membered macrolactone [84] (Scheme 36). The
lack of a defined stereochemistry at C9 was nonrelevant for the total synthesis of
narbonolide 138, since compound 137 was further oxidized during the synthesis.
10.4 16-Membered Macrocyclic Lactones
10.4.1 Spiramycin I
An example for a 16-membered macrocycle using NHK coupling was presented
during the aglycone synthesis of spiramycin I 141 by using a large excess of
reducing CrCl 2 (100 equivalents) and a stoichiometric amount of NiCl 2 . Compound
Scheme 35 (+)-Brefeldin C, 135 by using an intramolecular NHK coupling
Scheme 36 Narbonolide, 138 by using an intramolecular NHK coupling
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M. Cordes and M. Kalesse