Claviciptic acid

The palladium catalyzed intramolecular nucleophilic substitution of allyl alcohol derivatives (Tsuji-Trost reaction) has successfully been extended to the closure of a seven membered ring. The coupling of the allyl alcohol unit and the enamide was the key step in the preparation of the natural product claviciptic acid (5.14.),14... 

Electrochemical reduction of the pyridinium compounds (22, R = H, Bu1), prepared by reaction of 6-bromohexan-2-one and the respective pyridine, yields mixtures of the the fused azepines (23) and (24), albeit in low yield <95aG(K)2007>. A new synthesis of claviciptic acid has been published <95Joci486>. 

Examples of specialized uses of palladium-catalyzed Heck reaction include the synthesis of the ergot metabolite claviciptic acid, where two sequential vinylations were carried out by taking advantage of the greater reactivity of a 3-iodo over a 4-bromo substituent (Scheme 127) <87JA4335>. 

Claviciptic acid Combinational use of 4-selective lithiation of l-(triisopropylsilyl)gramine and fluoride ion induced elimination-addition reaction of 4- [( )-3-hydroxy-3-methyl-1 -butenyl] -1 -(triisopropylsilyl)gramme [31]... 

After installation of the stereogenic center and further manipulations, (—)-cis-claviciptic acid 32 was obtained in 20% yield and with 99% ee (Scheme 5). 

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