Viruses overall reaction

An unusual example of oxazoline formation is illustrated in the following example in which the hydroxyl moiety is masked as a tetrahydrofuran ring. Depending on reaction conditions, regioselective ring closure to one of the two oxazolines can be realized. Thus, addition of methanesulfonyl chloride to a mixture of substrate and EtsN resulted in the expected oxazoline 46. On the other hand, addition of < 1 equiv of triethylamine to a mixture of substrate and methanesulfonyl chloride, followed by acid catalysis produced oxazoline 47. Intermediate 47, obtained in 72% overall yield from 45, was susequently converted to the human immunodeficiency virus (HlV)-protease inhibitor Nelfinavir 48 (Scheme 8.18). 

The risk of a pandemic caused by influenza viruses such as the avian H5N1 virus has recently raised the profile of the anti-influenza neuraminidase inhihitor (—)-oseltamivir (163). Several novel synthetic methods to access the natural product have been proposed [62]. An outstanding approach is the enantioselective total synthesis reported by Hayashi and coworkers [63], in which the natural product was obtained after two one-pot sequences, featuring a domino reaction, in 60% overall yield (Scheme 14.24). Utilizing a-alkoxyaldehyde 155 and nitroalkene 156, the first sequence commenced with an organocatalytic asymmetric Michael... 

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