Oxazolo pyrimidin-7-ones

Oxazolo[4,5-6]pyridin-2(3 H)-one IR, 6, 653 <76HCA1593) Oxazolo[4,5-fi]pyridin-2(3H)-one, 3-(4-chlorophenyl)-3a,7a-dihydro-6-methyl-X-ray, 6, 647 <79CPB2261) Oxazolo[4,5-6]pyridin-2(3H)-one, 3-(4-chlorophenyl)-3a,7a-dihydro-7a-methyl-X-ray, 6, 647 <79CPB2261) 5H-Oxazolo[3,2-a]pyridin-3(2H)-one, 2-phenyl-6,7,8,8a-tetrahydro-X-ray, 6, 646 <77MI42902) Oxazolo[5,4-d]pyrimidin-4-amine, A7-methyl- H NMR, 6, 650 <70BCJ3909)... 

H,4H-Oxazolo[5,4,3-y]pyrido[3,2-g]quinolin-4-one, 8-hydroxymethyl-6-methyl — see Nybomyein 5H-Oxazolo[2,3-[Pg.731]

Chloro-2,3-dihydro-7-(hydroxymethyl)-3,3-dimethyl-5//-oxazolo[3,2-a]pyrimidin-5-one, see Terbacil 6-Chloro-2,3-dihydro-7-methyl-3,3-dimethyl-5//-oxazo lo[3,2-a]pyrimidin-5-one, see Terbacil Chlorodihydroxybiphenyl, see TCDD... 

Plant The major degradation products of [2- C]terbacil identified in alfalfa using a mass spectrometer were (% of applied amount) 3-/er/-butyl-5-chloro-6-hydroxymethyluracil (11.9) and 6-chloro-2,3-dihydro-7-(hydroxymethyl)-3,3-dimethyl-5//-oxazolo[3,2-a]pyrimidin-5-one (41.2). Two additional compounds tentatively identified by TLC were 3-/er/-butyl-6-hydroxy-methyluracil and 6-chloro-2,3-dihydro-7-methyl-3,3-dimethyl-5//-oxazolo[3,2-a]pyrimidin-5-one (Rhodes, 1977). 

Oxazolo[5,4 3,4]pyrido[ 1,2-a ]pyrimidin-4-one 496 was prepared in the reaction of 8-amino-9-hydroxy-2-methyl-4//-pyrido[ 1,2-a]pyrimidin-4-one 327 and acetic anhydride for 24 hours (92KGS1660). 

Substituied-4a-hydroxy-9//-cycloalkvl 1.2-< oxazolo 3,2- ]pyrimidin-9-ones (40) have been prepared by cyclocondensation of 5-substituted-2-amino-2-oxazolines (39) with ethyl 2-oxocyclohexanecarboxylate.64... 

JOC6700). The 1-methyl derivative of 231 (R1 = Me) was accompanied by 10% of the C-l epimer. Reduction of oxazolo[3,2-a]pyrimidine-5-carboxylates 232 with Zn(BH4)2 gave an epimeric mixture of 4-phenylper-hydropyrido[2,l-c][l,4]oxazin-l-one (233) (94JOC3769). When 232 reacted with BF3-etherate at -10°C in THF, then with Grignaird reagents at -78°C, epimeric mixtures of 4-phenyl-6-substituted perhydropyrido-[2,1 -c] [ 1,4]oxazin-1 -ones (234) were isolated after treatment with 2N HC1. 

N-Alkylation in the azine ring is demonstrated by the preparation of 2-substituted 6-(jS-D-ribofuranosyl)oxazolo[5,4-rf]pyrimidin-7(6/T)-ones (181). In this case the silyl ether variant of the Hilbert-Johnson method for the synthesis of pyrimidine nucleosides has been used the pyrimidinone (180) is converted into its silyl ether using HMDS and the ether reacted with 2,3,5-tri-O-acetyl-D-ribofuranosyl bromide under Hg(II) catalysis. Deacetylation using methanolic ammonia gives the nucleoside with a /3-anomeric configuration (74JMC1282). 

Azine approach. 2-Substituted oxazolo[5,4-c ]pyrimidin-7-ones (236) are formed when 5-amino-4,6-dihydroxypyrimidines are heated with acid anhydrides (71JHC503,75JOC3141). 

Azole approach. A one-pot synthesis of substituted 2,3-dihydro-5-oxo-5H-oxazolo[2,3-b ]quinazolines (273) consists of reacting esters of anthranilic acid with a 2-chloro- or 2-bromoalkyl-isocyanate the initially formed urea (271) is cyclized to the acid salt of the oxazoline (272), which on addition of piperidine as base forms the pyrimidine ring (76S469). In a similar reaction the aziridinyl urea (274), which is available from aziridinyl isocyanate... 

Tetrahydro-7H-oxazolo[3,2-a]pyrimidin-7-ones (275) can be prepared from 2-amino-2-oxazolines and a,/8-unsaturated carboxylic esters. The orientation of the substituents in the reaction product corresponds to Michael addition of the oxazoline nitrogen as the first step (74LA593). 

Hexahydro-l-phenyl-3jFf-oxazolo[3,4-a]pyridin-3-imines (292) have antihypotensive and central nervous system stimulant activity which is stereochemically dependent. Most active is the (-)-trans form of the parent compound (292 R = H, Ar = Ph) (80MI42902). Useful stimulant activity for the central nervous system has also been claimed for 2,3,5,6-tetrahydro-7H-oxazolo[3,2-a]pyrimidin-7-ones (74GEP2253555) and quinazoline homo-logues (293) (74GEP2252122). 

Oxazolo[5,4-6]pyridine, 704, 906 Oxazolo[3,2-a]pyridin-5-one, 918 Oxazoio[4,5-6]pyridin-2-one, 716, 1226 Oxazoio[4,5 [Pg.774]

Oxazolo[3,2-a pyrimidin-4-ium, 807 Oxazolo 5,4-d]pyrimidin-7-one, 714 Oxazolo[4,5-b]quinolin-2-one, 1226... 

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