Macrolactonisation reaction

As part of their investigations towards the synthesis of the cytotoxic marine natural product diazonamide A, Feldman et al. discovered a noteworthy atroposelective macrolactonisation reaction. Thus, the ring closure of the configurationally flexible model bisindole depicted in Scheme 5.29 afforded the corresponding lactone as a single isomer. The bulk of the NB0C2 group was... 

Several reaction were examined the dehydrobromination of bromoalkanes, the esterification of benzoic acid with 1-bromobutane and the macrolactonisation of [Pg.138]

Other approaches to make macrocyclic ring systems exist as well. Smith and Ott prepared the central framework of (-)-macrolactin A by using a Mitsunobu reaction to prepare a linear precursor for the final ring closure reaction with a Stille reaction. The Mitsunobu reaction proceeded in 74% yield the Stille reaction, in contrast, took seven days and provided the desired macrocyclic intermediate 60 in 42% yield. In an inverse approach, Williams and Meyer prepared (+)-amphidinolide K by preparing a seco-acid macrolactonisation precursor via Stille reaction and then using the Mitsunobu reaction to close the ring to form 61. ... 

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