17.2 12-Membered Macrocyclic Lactones
17.2.1 Aplysiatoxin
The potential of the Boden–Keck procedure was rapidly recognized and used in a
large number of total syntheses, for example, in the synthesis of 220, a
12-membered precursor of aplysiatoxin 221 [143] (Scheme 62).
17.3 13-Membered Macrocyclic Lactones
17.3.1 Diazonamide A
A remarkable example of a 13-membered macrocyclization has been documented
in the synthesis of diazonamide A-related biaryl 223. For that, phenoxy acid 222
was cyclized by treatment with Keck’s modified Steglich esterification conditions
to furnish lactone 223 in good yields [144] (Scheme 63).
17.4 14-Membered Macrocyclic Lactones
17.4.1 (–)-Colletol
In the first total synthesis of the unsymmetrical bis-macrolide (–)-colletol 226 [145]
(Scheme 64), the penultimate step also utilized Keck’s macrolactonization to
assemble the 14-membered ring in excellent yields (71 % overall yield).
Scheme 62 The Boden–Keck protocol in the total synthesis of aplysiatoxin, 221
Synthesis of 12- to 16-Membered-Ring Lactones
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