InChI=1/C18H22NO3P/c1-2-3-7-15-10-11-17(14-23(21)22)19(12-15)13-18(20)16-8-5-4-6-9-16/h4-6,8-12,23H,2-3,7,13-14H2,1H pyridinium, 5-butyl-2-[(hydroxyphosphinyl)methyl]-1-(2-oxo-2-phenylethyl)-, inner salt {[5-butyl-1-(2-oxo-2-phenylethyl)pyridinium-2-yl]methyl}phosphinate