2- Amino-5//-pyrazino pyrido

Structures of 3-[(4-methylphenyl)amino]-47/-pyrido[l,2-tf]pyrazine-4-thione, iV-tosyl-3-[(4-methylphenyl)a-mino]-4//-pyrido[l,2-tf]pyrazine 4-imine, and 246 were confirmed by X-ray investigations <1999JPR332>. The stereostructures of (4A,llaA)-lla-ethoxycarbonylT,3,4,6,lla-hexahydro-l,3,4,6,ll,lla-hexahydro-4-methox-ycarbonyl-l-oxo-[l,4]oxazino[4,3-A isoquinoline <1995ZK787>, 2//-pyrazino[l,2- ]isoquinolinc-l,4-dione 247 <2001TL543>, 4-benzyl-2-methyl-1,3,4,6,7,11 b-hcxahydro-2//-pyrazino[2,l -zz] isoqu incline-3,6-dione... 

Stereostructures of a co-crystal of (li )-l- 4-[(9aA)-perhydropyrido[l,2- ]pyrazin-2-yl]phenyl -2-phenyl-7-hydroxy-l, 2,3,4-tetrahydroisoquinoline with ERa-LBD301-553/C — S triple mutant <2005JME364> and iV-[2-(4-hydroxyphenyl)ethyl]-a-propyl-3-[(4-hydroxyphenyl)methyl]-l,4-dioxo-l,2,3,4,ll,l la-hexahydro-67/-pyrazino[l,2- ]isoquinoline-3-acetamide with fructose-1,6-biphosphatase <2003JBC51176> were determined by X-ray crystallography. The structure of a complex formed from 3-[( -methylphenyl)amino]-4-[(4-methylphenyl)imino]-4//-pyrido[l,2-tf]pyrazine with sodium bis(trimethylsilyl)amide and (norbornadiene)Mo(CO)4 in THF was characterized by single crystal X-ray diffraction <1995JPR38>. 

Heating a mixture of 2-amino-3-nitroso-4//-pyrido[ 1,2-a]pyrimidin-4-one, potassium cyanide, and ethyl cyanoacetate afforded 2-amino-5//-pyrazino[5,6-e]pyrido[l,2-a]pyrimidin-5-one 708 (92MI23). 

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