The synthesis and single-crystal X-ray structure determination of a new cage
molecule containing four oxygen, two sulfur, and two nitrogen heteroatoms are
described. The structure determination shows that a twist occurs about each
(tribenzyl) nitrogen bridgehead so that an overall helical configuration
within putative quasi-2 symmetry is generated; both nitrogens have their lone
pairs orientatedexo. Single crystals of this compound
are homochiral. Semiempirical MO calculations have been used to probe the
topological rigidity of this system relative to the more symmetrical analogue
incorporating six oxygen and two nitrogen heteroatoms reported previously. The
introduction of the sulfur atoms appears to restrict the facile
interconversion between enantiomers that was predicted for the
N2O6-analogue mentioned above. The
implications of the structure for the design of larger cages are discussed.
Semiempirical MO calculations for double-strand DNA and its base-mismatched ones