by De Brabander et al. [67] and Rizzacasa et al. [68, 69] in the synthesis of
benzolactone apicularens (ten-membered). It takes advantage of the loss of acetone
followed by alkylation.
6.2 12-Membered Macrocyclic Lactones
6.2.1 Salicylihalamides A and B
The base-induced macrolactonization of benzodioxinones to benzolactones has
been used in the synthesis of salicylihalamides A, 65 and B, 66 [70] (Scheme 26).
7 Macrolactones via Intramolecular Yamamoto et al.
Vinylogous Aldol Reaction
7.1 Background
An intramolecular version of the Yamamoto vinylogous aldol reaction [71] is the
macrocyclization process for the construction of 12- and 14-membered macrolides.
The yields are high (up to 89 %), and the reaction can proceed with excellent remote
stereocontrol (dr up to >25/1) with chiral substrates [72] (Scheme 27). This
Scheme 25 Base-induced macrolactonization of benzodioxinones to benzolactones
Scheme 26 Base-induced macrolactonization during the formal total synthesis of
salicylihalamide A, 65 and salicylihalamide B, 66
Synthesis of 12- to 16-Membered-Ring Lactones
391