M. Egli, A. Dreiding
Sep 10, 1986
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0
Influential Citations
17
Citations
Journal
Helvetica Chimica Acta
Abstract
Synthesis of Racemic Aminosugar Lactones: xylo- and lyxo-2,3-Diacetylamino-5-acetoxypentan-4-olide and -2,3,5-Triacetylaminopentan-4-olide Starting with 5-hydroxy-2-penten-4-olide (1), the tricyclic intermediate 4 was prepared via the chloride 2, the acyl azide 3, and an intramolecular nitrene addition (Scheme 3). Azide ion opened the aziridine ring in 4 at C(α) to give 5, which was transformed via7 into one of the title compounds, the triacetylated diamino-hydroxy-lactone 13 (Scheme 4). An alternative conversion of 4 into 13 involved the synthesis of the N-acetylaziridine 10, the opening of the 3-ring of 10 with N to form 12, and a final reductive acetylation (Scheme 5). The third N-substituent was introduced at C(δ) of 13 by the following sequence: hydrolysis of the AcO group (14), mesylation (15), substitution by N ( 16), and reductive acetylation to yield the other title compound, the triacetylated triaminolactone 17 (Scheme 6). Since the ring opening of aziridines by nucleophiles occurs by inversion, the primary products 5a and 12a of the N reactions as well as the substances derived from them, i.e.6a, 7a, and 13a-17a, have the xylo-configuration (a-series). Under some of the reaction conditions, the primary xylo-products suffered a partial epimerization at C(α) to yield mixtures containing the corresponding lyxo-products (b-series): The equilibrium between the xylo- and lyxo-isomers was estimated for 5a/5b=1:3, 12a/12b=5:2, 13a/13b=3:1, and 16a/16b=2:1. Since the stereoisomers of the a- and the b-series were always separable, the other lyxo-products, i.e.6b, 7b, could be prepared from 5b and 12b.