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1.
Uracil and thymine react with benzoyl chloride in acetonitrile-pyridine solution at room temperature to give first their 1--benzoyl (2b and 3b) and then their 1-, 3--dibenzoyl derivatives (4a and 4b, respectively); the latter compounds are converted into the corresponding 3--benzoyl derivatives (5a and 6a) under mild conditions of basic hydrolysis. 相似文献
2.
Methods were developed to prepare 1 -methyl-, 3-methyl- and 4-0-methyl-ψ-isocytidine by selective methylation.35O-Tetraisopropyldisiloxanyl-ψ isocytidine (8) was trimethylsilylated and then treated with MeI and, after deprotection, 1 -methyl-ψ isocytidine (6) was obtained. The 2deoxy analog (7) was also prepared in a similar manner from the 2deoxy analog (10) of 8. Treatment of 8 with CH2N2 afforded the 3-methyl-ψ-isocytidine derivative (19) as the major product. Methylation with diazomethane also occurred mainly on N3 of the 2deoxy analog 10 to form 20. Removal of the 3 5O-protecting group from 19 and 20 afforded 3-methyl-ψ-isocytidine (14) and its 2-deoxy analog (15), respectively. 2-N-Acetyl- 35O-tetraisopropyldisiloxanyl-ψ-isocytidine (24), on the other hand, gave the 4-O-methyl derivative (25) as the major product upon CH2N2 treatment. Subsequent deprotection of 25 afforded 4-O-methyl-ψ-isocytidine (29). aiv51b1p33b 相似文献
3.
Depending upon the experimental conditions, t-butyl (1,5,7,8)-1-ethoxycarbonyl-8-hydroxy-2-oxa-6-azabicyclo[3.2.0]octane-7-carboxylate (2a) reacts with methanesulphonyl chloride to give predominantly the -methanesulphonyl derivative (2b), the -methanesulphonyl derivative (3a), or the -(methanesulphonyl)methane-sulphonyl derivative (6a). 相似文献
4.
The synthesis of 2,4-dimethoxypyrrolo[3,2-]pyrimidine () is described. This facile, 3-step synthesis involves the bromination of 2,4-dimethoxy-6-methyl-5-nitropyrimidine (), and the subsequent conversion of compound into compound . 相似文献
5.
In contrast with the reaction of α-aminonitriles a, the corresponding -acylated α-aminonitriles b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles - or 4(5)-imidazolones , the latter being converted in some cases into imidazo [2,1-]isoquinoline-2,5,6(3)-triones. Reactions of compounds b-f and ethyl chlorooxoacetate provide evidence for a 5(4)-iminooxazole intermediate , which aromatizes to yield 5-aminooxazoles -; however, unaromatizable īntermediates of type - isolable as 5(4)y-oxazolones after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives . 相似文献
6.
Claudio Fuganti Piero Grasselli Giuseppe Pedrocchi-Fantoni 《Tetrahedron letters》1979,20(26):2453-2454
Feeding experiments with (4) [5-3H;5-14C]-leucine () and with the (4) [5-3H;2-14C]-isomer () show that incorporation into the isoprenylated tryptophan derivative echinuline (), produced by , involves, to a large extent, loss of the fragment enbodying the carbon atom at position 2 of the fed amino acid. 相似文献
7.
Two novel nucleosides, mycalisines A and B, have been isolated from a marine sponge and their structures elucidated as 4-amino-5-cyano-7-(3--methyl-5-deoxy-β-D--pent-4-enofuranosyl)-pyrrolo[2,3-]pyrimidine and 5-cyano-7-(3--methyl-5-deoxy-β-D--pent-4-enofuranosyl)-pyrrolo[2,3-]pyrimidine-4-one, respectively. Both compounds inhibit cell division of fertilized starfish eggs. 相似文献
8.
Reaction of benzilmonohydrazone(1) with S4N4 gives the azine (6) and not the 2--imidazole (2); this invalidates the claim that (2) is not the intermediate in the formation of -benzoyltriphenylimidazole from benzil and ammonia. S4N4 converts diphenylketene into thiobenzophenone. 相似文献
9.
A tritriacontanucleotide which has the sequence of the 5half molecule of E.coli glycine tRNA2, was synthesized by the phosphotriester method involving p-anisidate protection for the 3phosphate ends. Di- and trinucleotide units were prepared from 5dimethoxytrityl-2O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 35unprotected nucleosides followed by phosphorylation to give 3phosphodiester blocks. The 3terminal dimers and trimers were synthesized by using 3(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5deblocking of larger fragments. Finally a 3phosphodiester block with a chain length of 20 was condensed with a 5OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2. 相似文献
10.
As synthetic precursors of hexaaza-kekulene 1 the dibenzo[]= [1,10] phenanthroline systems 2, 3, 4, 5 and 6 were prepared. From 6 via 7 a product was obtained for which the dodecahydrohexaaza-kekulene structure 8 is suggested on the basis of 1H-NMR comparison with the dipyrido[3,2-;=2′,3′-]acridine (14) for which two syntheses are reported. 相似文献
11.
The structure of piplartine (=piperlongumine) was established as ()--3',4',5'-trimethoxycinnamoyl-5,6-dihydro-2(1H)-pyridone () by synthesis and by an X-ray crystallographic analysis. Model condensation of ()-3,4,5-trimethoxycinnamoyl chloride and crotonamide gave not the expected cinnamoylcrotonamide, but ()--3', 4', 5' -trimethoxycinnamoyl-3-chlorobutyramide (). 相似文献
12.
6--leukotrienes C and D (3 and 4) have been synthesized unambiguously via the 5(), 6()-epoxide (5,6-) which is isomeric with leukotriene A. These 6--leukotrienes are less active (especially 4) than leukotrienes C and D (1 and 2) and have not been found in substantial quantity in natural SRS sources. 相似文献
13.
Felix H. Cano Concha Foces-Foces Manuel Bernabe Jesus Jimenez-Barbero Manuel Martin-Lomas Soledad Penades-Ullate 《Tetrahedron》1985,41(18):3875-3886
X-Ray and 1H N.M.R. studies on pyranoid rings 1,2--fused to dioxolane rings in acetylated -gluco- and --galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the -gluco but not in the -galactopyranose series. The crystal structure of 3,4,6-tri--acetyl-1,2--(R)--(l-cyano-ethylidene)-α--glucopyranose () and 3,4,6-tri--acetyl-1,2--()-(1-cyano-ethylidene)-α--galactopyranose ()have been determined by X-ray analysis. Lattice parameters for are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened 4C1 and that of the dioxolane ring as distorted E1. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The 1H N.M.R. spectra of and and 3,4,6-tri--acetyl-1,2-O-(S)- and (R)-ethylidene-α--glucopyranose ( and ), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ()-ethylidene-α--galactopyranose ( and ), and 3,4,6-tri--acetyl-1,2--()-and ()-benzylidene-α--glucopyranose ( and ) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the -gluco series , and may be described as flattened 4C1 and that of and as 25. The major solution conformation of the pyranoid ring in all compounds in the -galacto series (,,,) may be described as flattened 41. 相似文献
14.
A. Zanarotti 《Tetrahedron letters》1982,23(38):3963-3964
Vinyl quinone methide () reacts with polyphenols to give cinnamylphenols () and neo-flavanoids (). Oxidation of cinnamylphenol (b) leads to malvidin () via the isolated intermediate flav-3-en-3o1 (b). 相似文献
15.
3-(t-Butoxycarbonyl)-2-(trifluoromethyl)imidazo[1,2-]-pyridine, prepared from trifluoroacetonitrile and pyridinium t-butoxycarbonylmethylide, reacts smoothly with trifluoroacetic acid to provide 2-(trifluoromethyl)imidazo[1,2-]pyridine-3-carboxylic acid, which gives 2-(trifluoromethyl)imidazo[1,2-]-pyridine when heated. 3-Cyano-2-(trifluoromethyl)imidazo[1,2-]pyridine can be obtained treatment of trifluoroacetonitrile with pyridinium cyanomethylide, which is sufficiently reactive to effect nucleophilic displacement of fluorine from pentafluoropyridine under mild conditions [→pyridinium cyano(tetrafluoro-4-pyridyl)methylide]. 相似文献
16.
- The corresponding - and -methyl- and -benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines were synthesized from - and -methyl and-benzyl-2- aminomethyl-1-cyclohexanols , from - and -methyl- and benzyl -2-hydroxymethyl-1-cyclohexylamines by reaction with formaldehyde. The aminoalcohols and were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of -benzyl--4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate . determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy. 相似文献
17.
Ronald E. Banks Ismail M. Farhat Roy Fields Robin G. Pritchard Mohamad M. Saleh 《Journal of fluorine chemistry》1985,28(3):325-340
The nitrosoarenes ArNO (Ar = C6H5, 2-MeC6H4, 2,4,6- Me3C6H2 and C6F5) have been condensed with 4-(dichloroamino)- tetrafluoropyridine to provide the azoxy-compounds pyFN()Ar (pyF = 2,3,5,6-tetrafluoro-4-pyridyl); de-oxygenation of the first three with triphenylphosphine or triethyl phosphite gave the corresponding azo-compounds, and the reverse reaction was achieved in the case of pyFNNC6H2Me3-2,4,6 using peroxytrifluoroacetic acid. Thermolysis of 4-azidotetrafluoropyridine in the presence of pentafluoronitrosobenzene provided the perfluorinated azoxy-compound pyFN()C6F5. X-Ray methods have been used to determine the molecular geometry of pyFN()C6H2Me3-2,4,6. 相似文献
18.
Alkylation of the distal double bond of pseudoionone has been carried out with isoprene epoxide (ZnCl2 /MeNO2 ) leading directly to α-, α- and γ hydroxyprenylionones. The α- and γ-isomers have been converted in few steps into the C50 carotenoids decaprenoxanthin and C.p. 450 respectively. 相似文献
19.
Simultaneous presence of the salt and one of the lanthanide complexes (+)-, (+)-, or (+)- splits 1H or 13C NMR signals of the chiral alkenes , , and as well as of the chiral arene ; the enantiomeric purity of a mixture of (+)- and (?)- was determined successfully. 相似文献
20.
Single-crystal X-ray analyses have defined the structures and solid-state conformations of (±)-N-benzoyl-3-methylaminocycloheptanone [(±)-]and (+)-N-benzoyl-4-methylaminocycloheptanone [(±)]. Resolution of (±)-[4- methylaminocycloheptanone α 1-hydroxytropane]to yield the (+)-enantiomer. Identical in all respects with the free base from natural (+)-physoperuvine, was achieved via the di-p-toluoyl-(+)-tartrate salt. 相似文献