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Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Synthesis of novel 4'-carbon-substituted BCA derivatives based on radical cyclization
Hiroki Kumamoto1, Nonoko Takahashi, Tomomi Shimamura
1School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Abstract:
Synthesis of (+/-)-4'-carbon-substituted BCA analogues (3) was carried out. Stereospecific construction of the cis-disposed 4'-carbon-substituent and 5'-hydroxy-methyl group was secured by employing the bicyclo-[3.3.0]lactone 11 as a key intermediate, which was prepared by radical-mediated 5-exo-trig cyclization of the phenylselenomethyl ester 10. After manipulation of the double bond of 11, 6-chloropurine was introduced based on the Mitsunobu reaction of the allyl alcohol 15. Ammonolysis of the resulting carbocyclic nucleoside led to the adenine derivative 16. Saponification of the bicylic lactone furnished the 4'-carboxylic acid 17 which serves as a precursor for other 4'-carbon-substituted analogues.
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