Jh. Vanmaarseveen et al., TRANSFORMATIONS OF THE TETRACYCLIC SKELETON OF EUDISTOMINS BY NEIGHBORING-GROUP PARTICIPATION IN THE MITSUNOBU REACTION, Recueil des travaux chimiques des Pays-Bas, 114(1), 1995, pp. 27-34
Mitsunobu reaction mediated introduction of nitrogen nucleophiles into
trans 1-hydroxy eudistomins afforded in high yields rearranged produc
ts instead of the anticipated cis eudistomins due to neighboring group
participations. Transannular interaction in the 6,5,6,7-membered tetr
acyclic ring system of the sulfur atom in the 1,6,2-oxathiazepine ring
, to give a thiiranium ion containing intermediate, was followed by in
termolecular attack of the present nucleophiles to give a 6,5,6,6-memb
ered tetracyclic ring system, now with a 1,5,2-oxathiazine ring. Subst
itution of the hydroxyl group in a trans 1-hydroxy dethia carba eudist
omin derivative (i.e. with a 1,2-oxazepine ring) also gave rearranged
products due to transannular interaction from the bridgehead nitrogen
atom, to give via an aziridinium ion intermediate, products with a 6,5
,7,6-membered tetracyclic ring system containing an 1,2-oxazine ring.