2,3-Aziridino-2,3-dideoxy-d-ribono-γ-lactone 5-Phosphonate:  Stereocontrolled Synthesis from d-Lyxose and Unusual Aziridine Ring Opening

The synthesis of (1R,4S,5S)-N-(benzyloxycarbonyl)-4-[(diethoxyphosphinyl)methyl]-3-oxa-6-azabicyclo[3.1.0]hexan-2-one (23), a new member of the 2,3-aziridino γ-lactone family of compounds, was achieved in 15 steps from d-lyxose. Like all aziridino γ-lactones known so far, 23 reacted with a soft nucleophile (ethanethiol) to give exclusively the product of aziridine ring opening at C-2 (24). On the other hand, hard nucleophiles (alcohols) did not react directly with the aziridine ring of 23 but appeared to promote intramolecular attack of the aziridine ring at C-3 by the C-5 phosphonate group, resulting, after hydrolytic workup, in formation of the 2-amino-3-hydroxy-d-ribono-1,4-lactone derivatives 25 and 26, instead of the expected 2-amino-3-alkoxy-d-xylono-1,4-lactone derivatives.