M. Weber et al., 1,3-diaxial repulsion vs. pi-delocalization in the 7-Amino-2,4-diazabicyclo[3.3.1]nonan-3-one skeleton, HELV CHIM A, 84(3), 2001, pp. 571-578
(1R.5S,6S.8R)-6,8,9-Trihydroxy-3-oxo-2,4-diazabicyclo[3.3.1]nonan-7-ammoniu
m chloride hydrate(3Cl .H2O)and(1R.5S,6S.8R)-7-amino-6,8,9-trihydroxy2,4-di
azabicyclo[3.3.1]nonan-3-one (4) have been prepared. and their crystal stru
ctures have been determined from single-crystal X-ray diffraction data. Bot
h compounds consist of a bicyclic skeleton with the three N-atoms in an all
-cis-1,3,5-triaxial arrangement. Considerable repulsion between these axial
N-atoms is indicated by a significant distortion of the: two cyclohexane c
hairs and by increased N...N distances. The lone pair of the free amino gro
up of 4 is involved in intermolecular H-bonding and is turned away from the
adjacent carbonyl C-atom of the urea moiety. The structural properties tog
ether with the observed reactivity do not provide any evidence for an intra
molecular donor-acceptor interaction between the carbonyl C- and the amine
N-atom.