Shikimic acid Oseltamivir phosphate

The neuramidase inhibitor oseltamivir phosphate was discovered by Gilead Sciences and developed by Roche Pharmaceuticals under the name of Tamiflu (Scheme 5.13) to be used as an orally active antiviral compound for prevention and treatment of influenza infections. Because of the recent emergence of the avian flu, the demand for Tamiflu has gained momentum. Two industrially feasible syntheses are known, starting from (—)-shikimic acid and (—)-quinic acid, respectively (Scheme 5.13) [45]. 

Approaches to oseltamivir phosphate (1) that were independent of ( )-shikimic acid as the raw material were also evaluated. The furan-ethyl acrylate Diels-Alder approach is shown in Scheme 7.8 (Abrecht et al., 2001, 2004). The zinc-catalyzed Diels-Alder reaction between furan and ethyl acrylate was heated at 50°C for 72 h to provide a 9 1 mixture favoring exo-isomer rac-43 over the enJo-isomer. The enJo-isomer was kinetically preferred, but with increased reaction times an equilibrium ratio of 9 1 was achieved favoring the thermodynamically preferred exo-isomer rac-43. The optical resolution of rac-43 was achieved via enantioselective ester hydrolysis using Chirazyme L-2 to give (—)-43 in 97%... 

In most cases, the Oseltamivir phosphate syntheses are based on (-)shikimic acid (fermentative production from glucose using a strain of e.coli). A novel synthesis route "" has been published recently that obviates this raw material and uses TMS A on the easily accessible component 1,4-cyclohexadiene. 

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