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1.
(±)-7-Deoxy-4-demethoxydaunomycinone(±)-) was cleanly resolved by forming a mixture of the diastereomeric acetals ((?)- and (+)- or (+)- and (?)- with the title -diol((+)- or (?)-) to give optically pure (R)(?)-. The method for racemizing the undesired enantiomer((S)(+)-) was also explored. Optically pure (+)-4-demethoxydauno-mycinone ((+)-) was elaborated from (R)(-)- according to the reported reaction scheme. 相似文献
2.
Reduction of the racemic α-hydroxy ketones((±)-) with fermenting baker's yeast followed by fractional recrystallization and oxidation was found to readily afford optically pure anthracyclinone intermediates((R) (?)- and their partially optically active antipodes ((S)(+)-). The useless enantiomers ((S)(+)- and diastereomeric -diols((+)- ) could be recycled to (±)- and the achiral ketones() by racemization and oxidative cleavage, respectively. 相似文献
3.
The syntheses of 5-methyl-5,8,9,14-tetrahydroindolo(2,3-)indolo (2,3-) quinolizin-6-one and 15-methyl-7,8,13,15-tetrahydroindolo ( 3,2-) indolo(2,3-)quinolizin-5-one from the photochemical cyclisation of i-methylene-2-(N-`methylindole-2'-carbonyl) 1,2,3,4-tetrahydro-B-carboline and 1-methylene-2- (N-`methylindole-3' carbonyl) 1,2,3,4,-tetrahydro-B-carboline are described. Attempts to prepare indolo(2,3-)isoquinolines from the photochemical cyclisation of 2-benzamidoindoles were unsuccessful. 相似文献
4.
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
5.
Ratna Dasgupta Pranab R. Kanjilal Swapan K. Patra Manish Sarkar Usha Ranjan Ghatak 《Tetrahedron》1985,41(23):5619-5625
The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4--methoxyphenylbicyclo [2.2.2] octan-2-one () and 4--methoxyphenylbicyclo [2.2.2] octan-2-one () from easily accessible starting materials. The carbinol , derived from , undergoes facile rearrangement leading to 1--methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene (), which has been transformed to -1--methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one (). 相似文献
6.
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
7.
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
8.
Adenosine cyclic 3′,5′-phosphoramidate was synthesized by reacting adenosine cyclic 3′,5′-phosphate with POCl3, in trimethyl phosphate for 1 h at O°C, followed by in situ treatment of the reaction mixture with a suspension of (NH4)2CO3 in anhydrous DMF or pyridine or DMF/pyridine mixture for 30 min at 25° C. Diastereoisomers (P)- and (P)- the relative quantities of which depended on the solvent of (NH4)2CO3 treatment, were separated by reversed phase partition chromatography. Hydrolysis of (RP)- and (SP)- proceeded with predominant (90% in 0.1 N HCl, 100% in 0.1 N NaOH) -P-O-C bond breaking. 相似文献
9.
Giovanni Fronza Claudio Fuganti Piero Grasselli Giuseppe Pedrocchi-Fantoni 《Tetrahedron letters》1981,22(50):5073-5076
The synthesis of the N-benzoyl derivatives of - (10),- (13) and - (-vancosamine) (12) 2,3,6-trideoxy-3--methyl-3-aminohexose from the (2,3) diol (1) prepared in fermenting bakers' yeast from α-methylcinnamaldehyde and acetaldehyde is reported 相似文献
10.
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
11.
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
12.
Maurizio Botta Francesco De Angelis Gabriella Finizia Rosario Nicoletti Maurizio Delfini 《Tetrahedron letters》1985,26(28):3345-3348
Transformation of 6- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones (1a and 1b) into 1--acylated-pyrimidine derivatives 3(-) under Friedel-Craft like conditions is presented. In different acylation conditions 4-O-acylated-pyrimidines (5a and 5b) are also obtained. Compounds (3c) and (3f) can be directly converted into 1--acyl-protected-isouridine analogues (8a and 8b). 相似文献
13.
Reaction of ,,,-[9]annulene anion () with electrophiles (-) leads to substituted ,,,-1,3,5,7-cyclononatetraenes (-) which are precursors for the preparation of 10- and 10,10′-donor-substituted nonafulvenes (e.g. ). The influence of solvent and temperature on the 1H-nmr spectra of the nonafulvenes - has been investigated. 相似文献
14.
Combination of ()-4--butyldimethylsiloxy-2-cyclopentenone, ()-()-3--butyldimethylsiloxy-1-iodo-1-octene, and 6-methoxycarbonyl-2-hexynal via the tandem organo-copper conjugate addition—aldol reaction procedure leads directly to a 5,6-dehydroprostaglandin E2 derivative, which can be transformed to a variety of chiral primary prostaglandins in a stereoselective manner. 相似文献
15.
Roshantha A.S. Chandraratna Robert R. Birge William H. Okamura 《Tetrahedron letters》1984,25(10):1007-1010
The electronic absorption spectra of the four new 12---locked retinals (1a–1d) bearing 7-, 11- double bond geometries are described and compared with those of analogous 7-, 11--geometries (1e–1h) and parent retinals (2a-h). 相似文献
16.
Two new triterpenoid acids, designated as plectranthoic acid A and plectranthoic acid B, have been isolated from P. rugosus and are characterised as (20-S)-3α-hydroxy-18α,19α--urs-12-en-30β-oic acid and (14-S)-3α-hydroxy-18α, 19α -urs-12-en-27α-oic acid. 相似文献
17.
The title compounds (-) undergo facile base catalysed rearrangement to give -. A mechanism involving thioallylic rearrangement of intermediates, 2-bisalkylthiomethyl acrylophenones, (-) has been proposed. 相似文献
18.
(+)-Thalictrifoline () has been synthesized from an optically resolved (+)-8-oxo-13-carboxytetrahydroprotoberberine () whose absolute configuration was established by correlation with (+)-. This determines the absolute configurations of (+)-thalictrifoline () as 13R, 14R aria (+)-corydalic acid methyl ester () as 3R, 4R. 相似文献
19.
Upon irradiation a homologous series of certain phthalimides (-) possessing a terminal sulfide function in their N-poly-ether side chain undergo regioselective remote photocyclization affording seven to fifteen-membered crown ether analogs (-) in moderate yields. 相似文献
20.
- and -2-Methylamino and 2-benzylamino-3-hydroxymethylbicyclo [2.2.1]heptanes and the corresponding bicycio [2.2.1] heptenes ( -, -) were synthesized from β-amino acid esters containing the norbornane or norbornene skeleton (-). The aminoalcohols were converted to 5,8- methano -3,1-benzoxazines by reaction with formaldehyde. As established by 1H and 13C NMR spectroscopy, the predominant conformation is () for the , and () for the derivatives. 相似文献