3.4- Dihydro-lH,6H-pyrido

Methyl-3,4-dihydro-lH,6H-pyrido[l,2-c][l,3]oxazine-l,4-dione was identified in a hemodialysate uremic sample by the LC-MS/MS technique (09RCM3194). 

The treatment of 4-acetylpiperazinone 323 with LiHMDS, followed by addition of (C02Et)2 gave three condensation products 324-326. Upon addition of excess LiHMDS 8,9-dihydroxy-3,4-dihydro-lH,6H-pyrido [l,2-fl]pyrazine-l,6-dione 327 was obtained in low yield (07BML5595). The major isomer 324 could be izomerized into 325 on the action of TFA in aqueous MeCN, which readily cyclized to pyrido[l, 2-aJpyrazine-l, 6-dione 327. 14C-labeled 327 was also prepared using 14C-labeled diethyl oxalate. 

Reaction of 2-aminoethanol with cycloheptatriene-1,2,3,4,5,6,7-hepta-carboxylate 464 afforded 3,4-dihydro-lH,6H-pyrido[2,l-c][l,4]oxazine-1,6-dione 466 via 2(lH)-pyridone 465 (09TL5605). 

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See also in sourсe #XX -- [ , ]

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