Stereochemistry of fully acetylated tetrahydropterins and tetrahydroquinoxalines

Completely acetylated derivatives of naturally occurring tetrahydro-D-monapterin, (6R)-2-acetamido-6-[(1R,2R)-1,2,3-triacetoxypropyl]-5,8-diacetyl-5,6,7,8-tetrahydropteridin-4(3H)-one, show plus and minus CD signs at λ 280 and 240 nm, respectively. Similar CD spectra are obtained on (2S)-1,4-diacetyl-1,2,3,4-tetrahydro-2-isopropylquinoxaline and (2S)-1,4-diacetyl-1,2,3,4-tetrahydro-2-isobutylquinoxaline but not on (2S)-1,4-diacetyl-1,2,3,4-tetrahydro-2-methylquinoxaline nor on the 2-ethyl derivative. The similarity of their CD spectra is represented the same stereogenic structure based on the boat conformation confirmed by X-Ray crystallographic analyses.