11 アミノ糖合成の新しいアプローチ

概要

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A new method is reported for the synthesis of amino sugars such as daunosamine, 3-epidaunosamine, acosamine, and ristosamine, the sugar moieties of anthracycline antibiotics. The process consists of three key steps: (1) preparation of 2,3-dialkoxy-butanenitriles with the defined configuration, (2) introduction of C_2 unit into the nitriles, (3) reduction of β-aminoacrylates to create C-3 amino group having the desired stereochemistry. The first problem was dissolved by starting with L(+) tartaric acid and/or S(+) lactic acid. These were successfully transformed into (2S,3S)- and/or (2R,3S)-2,3-(alkylidenedioxy)butanenitrile. The second synthetic obstacle was kicked off by a new transformation of nitriles into β-aminoacrylates with the aid of the magnesium enolates of acetic acid esters. Final problem, stereoselective hydrogenation of the β-aminoacrylates, was accomplished by acetylation of the substrates followed by catalytic hydrogenation (1 atm) with PtO_2 catalyst in ethyl acetate solvent. Thus, (2S,3S)-2,3-(cyclohexylidenedioxy)butanenitrile was converted into N-acetyl-3-epidaunosamine methyl ether and the daunosamine derivative with ca 4: 1 ratio, whereas (2R,3S)-2,3-(cyclohexylidenedioxy)butanenitrile into acosamine derivatives with high degree of stereoselectivity.
天然有機化合物討論会の論文
1982-09-10