Synthesis of 6-Acetamido-5-amino- and -5-guanidino-3,4-dehydro-N-(2-ethylbutyryl)- 3-piperidinecarboxylic Acids Related to Zanamivir and Oseltamivir, Inhibitors of Influenza Virus Neuraminidases

[reaction: see text] 6-Acetamido-5-amino- and -5-guanidino-3, 4-dehydro-N-(2-ethylbutyryl)-3-piperidinecarboxylic acids (8 and 9) have been synthesized starting from natural siastatin B, a bacterial neuraminidase inhibitor isolated from Streptomyces culture in a stereospecific fashion. These compounds are related to zanamivir and oseltamivir, inhibitors of influenza virus neuraminidases.