Diterpenoid pyrones nalanthalide

Total Synthesis of Diterpenoid Pyrones, Nalanthalide, Sesquicillin, Candelalides A-C, and Subglutinols A, B... 

In this chapter, the total synthesis of biologically attractive diterpenoid pyrones— nalanthalide (1), sesquicillin (2), candelalides A-C (3-5), and sub-glutinols A (6), B (7)—has been summarized with particular focus on then-synthetic strategies. It is of interest to look at each respective method for approaching the target molecules. 

In the total synthesis of nalanthalide, the crucial coupling of the 7-pyrone moiety with the diterpenoid core was achieved by lithium halogen exchange of 3-bromo-2-methoxy-5,6-dimethyl-4/7-pyran-4-one 353 and addition of the resulting 3-lithio-7-pyrone 354 to aldehyde 355 to produce 356 in an impressive 87% yield (Scheme 53) <2005OL3745, 2006TL3251>. 

---