Danishefskys Synthetic Approach to Dynemicin

Unfortunately, synthesizing the test compounds for any of these reactions also constituted a formidable endeavor, since it meant that a route had to be identified that could provide substrates with 

With this critical reaction beautifully orchestrated, all efforts could now be directed towards closing the final juncture of the 10-membered enediyne ring, a requirement whose implementation was projected to involve the addition of an acetylide ion to a suitable group at C-7. However, since this operation would ultimately lead to the excision of the alcohol function at C-7, it was decided to use this motif productively for one additional operation before attempting its displacement, namely directing the formation of the central C3-C8 endocyclic epoxide. Thus, 49 was treated with mCPBA in buffered CH2CI2 at 0 C, giving rise to 50 in 88% yield with complete facial selectivity for the drawn product. Next, treatment of 50 with TB AF in THF at 0 °C, followed by silyl reprotection of the phenolic position under standard conditions (TBSCl, 

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