Spirotetronic Natural Products

A group of tetronic acid natural products with challenging structural patterns from both synthetic and biosynthetic viewpoints and interesting antibiotic and antitumor properties are the spirotetronic natural products. Tetrocarcin A (TCA) is produced by Micromonospora chalcea NRRL 11289 and possesses a polycyclic... 

Quartromicins are complex C2 symmetric macrocyclic natural products that have significant activity against a number of human viral targets.The diastereoselective synthesis of the endo- and exo-spirotetronate subunits of the quartromicins was accomplished by W.R. Roush and co-workers. The preparation of the exo-a-acetoxy aldehyde involved the Pummerer rearrangement oi a sulfoxide using acetic anhydride as the activating reagent and NaOAc as the co-catalyst. The yield of this transformation was modest and all attempts to improve its efficiency failed. 

In 2001, Kende s group [140] reported the first total synthesis of stemonamide and isostemonamide. Their synthesis took advantage of N-acyhminium ion chemistry for the construction of the spirotetronic core 274 (Scheme 1.41). The lack of stereoselectivity in the spirocycUzation step enables the formation of precursors 275 and 276 for both natural products. 

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