1.3- Oxazine-4,6-diones tetrahydro- from

Reaction of tetrahydropyridin-4-one 119 and l,r-carbonyldiimidazole furnished l,3,4,4n,5,6-hexahydropyrido[l,2-c][l,3]oxazine-l,6-dione 120 (99JA2651). Similarly, pyrido[l,2-c][l,3]oxazine-l-one 121 and [1,3] oxazino[4,3-n]isoquinoline-4-one 122 were prepared from the respective 2-(2-hydroxypropyl)piperidine and l-(2-hydroxypropyl)-1,2,3,4-tetrahy-droisoquinoline (99JOC3790). Reaction of a 2 1 diastereomeric mixture of l-(l,2-dihydroxyethyl)-6,7-dihydroxy-l,2,3,4-dihydroisoquinolines 123 and 124 with l,l -carbonyldiimidazole gave a 2.7 1 mixture of 1,9,10-trihy-droxy-l,6,7,ll/)-tetrahydro-2//,4//-[l,3]oxazino[4,3-n]isoquinoline-4-ones 125 and 126, which were separated on preparative TLC plate (99BMC2525). 

A series of enantiomerically pure tetrahydro-l//-pyrrolo[2,l-c][l,4]oxazine-l,4(3//)-diones 86a-d have been prepared by bromolactonization of acrylamides derived from proline mediated by NBS (Equation 5). These compounds... 

Two naturally occurring 1,3-oxazine derivatives with a unique, 2-chlorinated tetrahydro-l,3-oxazine structure were reported as metabolites isolated from extracts of the endophytic fungus Geotrichum sp. AL4 <2007MI1520>. Halogenated 3-(4-alkylphenyl)-l,3-benzoxazine-2,4(3//)-diones were found to exhibit antimycobacterial activity <2007AP264>. 

A novel acid-catalysed rearrangement of 2-hydroxy-2-phenylazo-y-butyrolactone (45) to the interesting /V-substituted tetrahydro-l,3-oxazine-2,4-dione derivative (46) has been reported.58 The photo- and thermo-chemistry of diazo(2-furyl)methane and diazo(3-furyl)methane have been investigated59 using matrix isolation techniques, and 3,7-diphenylpyrano[4,3-c]pyran-l,5-diones have been prepared60 from 5,5 -diphenyl-... 

R,9aR)-7-Azido-9a-methyl-4-phenyl-3,4,9,9a-tetrahydro-lH,6H-pyr-ido[2,l-c][l,4-oxazine-l,6-dione was obtained from (4R,9aR)-9a-methyl-4-phenyl-3,4,9,9a-tetrahydro derivative by addition of Br2 in boiling CCI4 for 2 h, then by stirring with saturated aqueous Na3S03 solution at room temperature, followed by the reaction with NaN3 in DMF at ambient temperature for 3 h and 70 °C for 4 h (09JOC4429). 

Photolytic or thermolytic cleavage of the N-0 bond of tetrahydro-1,2-oxazine-3,6-diones (407), followed by decarboxylation, gives intermediate 1,4-diradicals (408) which close to form 3-lactams (409), albeit in poor yields. Diradical intermediates analogous to (408) may be formed in the biosynthesis of isopenicillin N from trlpeptide precursors. In a similar vein, Easton has published full details of the synthesis of 3-lactams by ring contraction of isothiazolidinones, a reaction which may also be relevant to... 

Conventional methods have been used to prepare ribonucleoside analogues from 2-(l//)pyrazinone, 3,5-disubstituted pyridines (including a-anomers), 6-methyl-l,3-oxazine-2,4-dione and 6-methyluracil, 2-alkyl-4,5-dicarboxamido-imidazoles, 7-membered ring analogues (4) and (5) of uracil and tetrahydro-uracil [one diastereomer of (4) being the most potent inhibitor of cytidine deaminase yet discovered], 2-alkylthioadenine, 8-aza-3-deaza-guanine/ ... 

Tetrahydro-2H-6H-pyrimido[2,l-b]-l,3-oxazine-2,4-diones from tetr ahy dro-1 -malonyl-2 (IH) -pyrimidinones... 

Tetrahydro-l,3-oxazine-4,6-diones from azomethines and a-dicarboxylic acids... 

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