Bis(kojato)oxovanadium(IV) [abbreviated VO(ka)2], a close chemical analog of the insulin-mimetic
lead compound bis(maltolato)oxovanadium(IV)--abbreviated BMOV or VO(ma)2--is reported
and its reaction chemistry and insulin-mimetic properties are presented. VO(ka)2 [log
K1 = 7.61(10), log K2 = 6.89(6), log beta 2 = 14.50(16)] has a reaction chemistry
which directly parallels that of VO(ma)2. In aqueous solution it is more slowly oxidized
by molecular oxygen to [VO2(ka)2]- than is VO(ma)2 to [VO2(ma)2]-. Variable pH electrochemistry
and variable pH 51V NMR of solutions of VO(ka)2 are presented and contrasted with
the corresponding results for VO(ma)2. Time course studies (24 hr) in STZ-diabetic
rats following the oral or i.p. administration of VO(ka)2, VO(ma)2, VO2+ (vanadyl)
as vanadyl sulfate (VOSO4), and [VO2(ma)2]- as its [NH4]+ salt have been performed,
as have chronic oral studies comparing VO(ka)2 and VO(ma)2 over a six week period.
In all studies, the most potent form of vanadium was the neutrally charged, water
soluble, complex VO(ma)2.