D Timothy Anstine et al.
Monatshefte fur chemie, 145(7), 1117-1135 (2014-08-12)
Three new linear pentapyrrole rubinoid analogs: 2,3,7,8,17,18,22,23-octamethyl-12,13-bis-(2-carboxyethyl)-1,10,15,24,25,27,28,29-octahydro-27H-pentapyrrin-1,24-dione and 2,3,8,12,13,17,22,23-octamethyl-7,18-bis-(2-carboxyethyl)-1,10,15,24,25,26,27,28,29-octahydro-27H-pentapyrrin-1,24-dione, and its 7,18-dihexanoic acid analog were synthesized, respectively, from 2,3,7,8-tetramethyl-(10H)-dipyrrin-2-one, from 2,3,8-trimethyl-7-[2-(methoxycarbonyl)ethyl]-(10H)-dipyrrinone, and 2,3,8-trimethyl-7-[5-(methoxycarbonyl)pentyl]-(10H)-dipyrrinone. 13C NMR and 1H NMR measurements in (CD3)2SO confirmed the pentapyrrole structures, while 1H NMR data indicate