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1.
Hypervalent iodine oxidation of several flavanones (1a-1f) using (hydroxy(tosyloxy)iodo] benzene in methanol offers a new method for the synthesis of flavones (2a-2f). 相似文献
2.
A useful synthesis of 3-hydroxy-4-chromanone (6) is not currently available. Lead tetraacetate oxidation of 4-chromanone (4) yields the C(3) acetoxy derivative but this compound could not be deacetylated to 6.1 Recently Donnelly and Maloney reported2 that the Algar-Flynn-Oyamada reaction (H2O2/CH3OH/NaOH), which is commonly used for the conversion of o-hydroxychalcones (1) into 3-hydroxyflavanone (2) and 3-hydroxyflavones (3), does not yield 6 when applied to o-hydroxya-crylophenone 1 (R = H). The authors found that under less basic conditions using K2CO3 some 6 is formed but the major product is catechol. These observations clearly indicate the necessity of developing a method for making 6. The present note describes a staightforward way of preparing 3-hydroxy-4-chromanone (6) in good yield. 相似文献
3.
Ana Calvo-mateo María-José Camarasa Angel Díaz-Ortíz Federico G. De las Heras Antonio Alemany 《Journal of carbohydrate chemistry》2013,32(3):395-404
Abstract Aldol reaction of 1,2-O-isopropylidene-5-O-tertbutyl-dimethylsilyl-α-D-erythro-pentofuranos-3-ulose (1) with acetone in the presence of aqueous K2CO3 afforded 3-C-acetonyl-1,2-O-isopropylidene-5-O-tertbutyl-dimethylsilyl-α-D-ribofuranose(2). Similar reaction of 1,2:5, 6-di-o-isopropylidene- α-D-ribo-hexofuranos-3-ulose (3) afforded 3-C-acetonyl-1,2:5, 6-di-o-isopropylidene- α-D-allofuranose (4) and (1R, 3R, 7R, 8S, 10R)-perhydro-8-hydroxy-5,5,10-trimethyl-2,4,6,11,14-pentaoxatetracyclo[8,3,1,01,8,03,7] tetradecane. The stereochemistry of the new chiral centers were determined by 1H NOE experiments. 相似文献
4.
Muttaiya Sundaralingam Richard G. Brennan Panchanadam Swaminathan Tuli P. Haromy William B. Drendel James N. Bemiller 《Journal of carbohydrate chemistry》2013,32(1):85-103
Abstract The title compounds 1 and 2 (both C15O15NH21) crystallized in the monoclinic space group P21 (Z = 2) with a=8.864(1), b=8.346(1), c =13.569(1)Å, β =114.12(1), V=918.1(2)A3, D(calc) = 1.358 g/cc for compound 1, and a=15–045(1), b=8.106(1), c=7.491(1)Å, β =97.23(1)°, V=906.4(3)Å3 D(calc)= 1.375 g/cc, for compound 2. The structures were solved by direct methods and refined by the full-matrix least squares technique to R indices of 0.010 and 0.046, respectively. Both compounds are in the α ? D configuration and adopt the unusual 2C5, (1C4) chair conformation with the carbamoyl groups on the anomeric carbon atoms equatorially oriented. In this conformation the orientations of the substituents are 2e, 3a, 4a, 5a and 6a in 1 and 2e, 3a, 4a, 5e and 6a in 2 which leads to unfavorable 1,3-diaxial interactions. The “reverse anomeric effect” which induces the 2c5 chair conformation in these compounds, may have its origin in the unfavorable steric interactions found in the 5c2 (4C1) conformation where the carbamoyl group is axially oriented. Furthermore, the 2C5 conformation is stabilized by the N-H … O intramolecular hydrogen bond between the carbamoyl nitrogen atom and the pyranosyl ring oxygen atom. Semi-empirical energy calculations reveal that the rotational freedom of the carbamoyl group is greater for the equatorial orientation (2C5) than for the axial orientation (5C2). 相似文献
5.
Matthias Driess Walter Siebert 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract In the heterocycle (EtC)2(MeB)2S the sulfur atom may be replaced by a CR2 or a NR group; however, attempts to prepare the corresponding phosphorus compound via this route were unsuccessful. Also insertion of phenyl-phosphinidene [C6H5P] into the B-B bond of the 1,2-dihydro-1,2-diborete 2 (R1=N(CHMe2)2) failed. The reaction between the cis-diborylethene 3 (R1=N(CHMe2)) and C6H5PLi2 in C6H6 results in the formation of 1 in 84% yield. The yellowish compound can be sublimed, it is moderately stable in air due to electronic and steric shielding of the boron atoms by the amino groups. 相似文献
6.
We recently developed a convenient route to hexahydronaphthalenols such as 5 (R=CO2CH3 or CH3) starting from m-toluic acid (1)1. The key features of the route involved reduction-alkylation of the toluic acid to the dihydro derivative 2 2, subsequent deprotection and oxidation of the side chain primary alcohol, and acid-catalyzed cyclization of the resulting aldehyde 4. In the case of the dimethylnaphthalenols 5 (R=CH3), conversion of the angular carboxylic function to the methyl group was effected prior to cyclization via reduction of the p-toluenesulfonic ester of the neopentyl alcohol 3 (R=CH2OH) using lithium triethylborohydride3. 相似文献
7.
Thioacetamide has been used as an elegant sulphur transfer reagent for C-S-C coupling of reactive halides.1–4 Sulphur extrusion of biprotic carbothioamides to form corresponding nitriles has been reported with the help of (i) dichlorocarbene;5 (ii) triphenylphosphine, carbon tetrachloride, triethylamine;6 (iii) diethyl azocarboxylate, triphenylphosphine;7 and (iv) soft metal ions.8 Here, we report that under non-hydrolytic conditions viz. DMF/OEt, EtOH/OEt and DMF/Et3N, biprotic carbothioamides (1, R=CH3, C6H5, CH2C6H5) react with bromoacetophenone (2, Z=COC6H5), ethyl bromoacetate (2, Z=COOEt). 相似文献
8.
Danuta Mostowicz Czesław Bełzecki Marek Chmielewski 《Journal of carbohydrate chemistry》2013,32(4):805-810
Abstract Recently we have reported the addition of trichloracetyl isocuyanate to glycals 1 1,2,3. The reaction led to the highly stereoselective formation of a mixture of unstable [2+2] and [4+2] cycloadducts 2 and 3. The isocyanate adds to the glycal moiety anti to the substituent at C-3. The addition of benzylamine to the reac6tion mixture led to N-deprotection of 2 and allowed us to isolate stable bicyclic β-lactams 4 1-3. We have shown also that 2 (a mixture of α-L-gluco and β-L-manno isomers) obtained from L-rhamnal 1 (R1[dbnd]Ac, R2[dbnd]CH3 under high pressure, when treated with methanol, underwent a rapid trans opening of the four-membered ring to give respective glycosides 5(β-L-gluco and α-L-manno isomers). On the other hand 3 (R1[dbnd]Ac, R2[dbnd]CH3) under the same conditions added a molecule of methanol to the C[dbnd]N double bond affording 6. 相似文献
9.
Abstract Both anomers of methyl 1-thio-L-rhamnopyranosides were prepared through methylation of the corresponding isothiouronium salt. 2,3-0-Isopropylidene-, benzylidene-and the until now unknown diphenyl-methylene acetals were synthesized. Phase-transfer catalysed benzylation and LiA1H4-AlCl3-type hydrogenolysis of benzylidene acetals were used to obtain partially benzylated derivatives. Comparing the C NMR data of the synthesized compounds with those of their 0-glycoside analogues revealed that the 0→S exchanges at the anomeric centres caused drastic upfield shifts (~15 ppm) at C-1 and moderate downfield shifts at C-2 and C-5, as well. The chemical shift values of other carbons are not sensitive to the 0→S replacement. 相似文献
10.
Abstract Prolonged treatment of tetra-O-acetyl-1, 5-anhydro-hex-1-enitols (“tetra-O-acetyl-hydroxy-glycals”) 3 and 5 with BF3 in CH2Cl2 at RT lead to anomeric mixtures of the title compounds 2 and 4a, the α-anomer 4a dominating. Reaction of 5 gave the higher yields of 4a (71%) and 2 (12%), the results being accounted mechanistic grounds. The same reaction performed in an aromatic solvent, like toluene, gave rise to competing C-alkylation., The ortho and para-tolyl derivatives 6 and 7, also with enone structure, were isolated in a combined maximum yield of 40% from 5. β-Enone 2 was also prepared in moderate yield by thermolysis of β-d-glucopyranose pentaacetate (1). In this case no α-anomer 4a was detected. 相似文献
11.
Abstract The title compound 3, which is the first member of a new class of anhydroglycosides, was initially isolated from the methanolysis mixture of the pyranoid isomer 1 in about 1% yield. Improved yields of greater than 30 % of 3 are obtained by treating the main product of the aforementioned methanolysis, the dimethylacetal 2, with a catalytic amount of p-toluenesulfonic acid in boiling xylene. 3 (C7H12O5) crystallizes from diisopropyl ether in the monoclinic space group P21 (Z=2) with a = 552.4(1), b = 685.2(1), c = 1052.9(3) pm, α = 90.0, β = 98.95(6) and Y = 90.0°. The structure was solved by X-ray crystal structure analysis using direct methods to R indices of 0.036 and 0.045, respectively, for 1180 independent reflections. The furanoid ring in 3 adopts a conformation intermediate between 2T3(D) and E3(D) (puckering parameters: Q = 48.9 pm; Φ = 102.4°). The oxane ring adopts an a2Ca5(D) conformation, which is heavily distorted by flattening at C-6 (puckering parameters: Q = 64.2 pm; Φ = 58.1° and 0 = 159.5°). Orientation of the glycosidic methyl group is in accord with the exo-anomeric effect. The molecules of 3 are interchained in three dimensions by a system of hydrogen bonds. 相似文献
12.
Tsutomu Tsuchiya Yoshiaki Takahashi Makoto Endo Sumio Umezawa Hamao Umezawa 《Journal of carbohydrate chemistry》2013,32(4):587-611
2′,3′-Dideoxy-2′-fluorokanamycin A (23) was prepared by condensation of 6-azido-4-0-benzoyl-2,3,6-trideoxy-2-fluoro-α-D-ribo-hexopyranosyl bromide (13) and a protected disaccharide (19). Methyl 4,6-0-benzylidene-3-deoxy-β-D-arabino-hexopyranoside (5) prepared from methyl 4,6-0-benzylidene-3-chloro-3-deoxy-β-D-allo-hexopyranoside (1) by oxidation with pyridinium chlorochromate followed by reduction with Na2 S2O4 was fluorinated with the DAST reagent to give methyl 4,6-O-benzylidene-2,3-dideoxy-2-fluoro-β-D-ribo-hexopyranoside (7). Successive treatment of 7 with NBS, NaN3 and SOBr2 gave 13. The structure of the final product (23) was determined by the 1H and 19F and shift-correlated 2D NMR spectra. 相似文献
13.
Giovanni Frenza Claudio Fuganti Piero Grasselli Giuseppe Pedrocchi-fantoni 《Journal of carbohydrate chemistry》2013,32(3):225-248
Abstract The erythro and threo chiral C5 methyl ketones (4) and (5), prepared from the (2S, 3R)-methyl diel (1b), were converted into the phenylsulfenimines (6) and (7), which, in turn, on reaction with allyl-magnesiutn bromide, yielded after acid hydrolysis and benzoylation, the diastereoisomeric C8-N-aminodiol derivatives (9) and (11), with threo stereochemistry relative to positions 4 and 5. Ozonolysis of (9) and (11) yielded the l-arabino and l-xylo 3-O-methyl branched aminodeoxysugar derivatives (13) and (15), respectively. Using diallylzinc as the reagent, the diastereoisomeric erythro products (8) and (10) were obtained. The latter materials gave the l-ribo-and l-lyxo-(lL-vancosamine) derivatives (12) and (14) upon oxonolysis. The 1H and 13C NMR spectra of the four isomeric aminodeoxysugar derivatives (12)—(15) were discussed. 相似文献
14.
Rainer Bohlen Gerd-Volker Röschenthaler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):483-486
Abstract The properties of PF5, HPF4, H2PF3, and H3PF2 (Δ5[sgrave]5P derivatives of (HO)3PO, (HO)2HPO, (HO)H2PO, and of the hypothetic H3PO) and the formation of the related Δ5[sgrave]6P anions PF6 –, HPF5 –, and trans-H2PF4 – have been studied some years ago 1–4. The mono and spirocyclic dioxa and tetraoxa analogues, 1 and 2 available from the corresponding precursor phosphoranes by fluoride addition could be found also as products in the reaction of phosphite 35 and K+(CF3)2CFO– together with two other phosphates, 4 and 5. A 19F–19F homocorrelated 2 D NMR spectrum of 2 indicated coupling of the P–F fluorine nuclei with two CF3 groups by a non bond mechanism. 相似文献
15.
M. Brawner Floyd 《合成通讯》2013,43(6):317-323
Several recent publications2 report the synthesis of prostaglandin E1 (PGE1, 2) and some of its derivatives by conjugate addition reactions to ether-ester forms of hydroxycyclopentenone acid 1.3 The simplicity of this approach makes its application to the preparation of prostaglandins of the PG2- and PG3 - series (cis-Δ5)4 an attractive alternative to the existing elegant methods.5 We now wish to report a five-step synthesis of the requisite hydroxycyclopentenone precursor 3 from the readily available6 lactone 4. 相似文献
16.
Abstract Treatment of methyl 3,4-di-O-acyl-2,6-dideoxy-α-D-ribo-hexo-pyranoside 1 or 2 with trimethylsilyl halide leads to the formation of a complex mixture of α-D-ribo-hexopyranosyl halides 3 or 5 together with the educts 1 or 2 as well as their β-anomers 8 or 9. The bromides 3 and 5, suitable for glycosidations, are preferably obtained by reaction of the digitoxose acetate derivatives 6 and 7, respectively, which in turn are prepared from 1 and 2 by mild acetolysis. Further reaction of the halides 3 to 5 with trimethylsilyl halides gives rise to a quantitative formation of the 2,3,6-trideoxy-4-0-acyl-3-halo-α-D -arabino-hexopyranosyl halides 10 to 12. In another reaction sequence starting with the olivose triacetate 20 the formation of 10 via the halide 13 is demonstrated. Structural evidence for the halides 10 to 12 is given by 1H NMR data as well as by analyses of their glycosides 14 to 19. The results support a mechanistic interpretation for the formation of 10 to 12 via a 3,4-acetoxonium ion as the key intermediate obtained from 3 by an SNfi and from 13 and SN2i step. Final conversion into the terminal halodeoxy compounds 10 to 12 proceeds by and SN2 reaction with the halide ion. 相似文献
17.
S. Achi J. P. Genet S. Juge Ph. Potin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract The asymmetric synthesis of phosphinous compounds from diheterophosphacycloal kane-1,3,2 was investigated in a transition metal complex series. Complexes 1 and 2 were prepared from diaminophosphine, (?)-ephedrine and W (CO)5 THP (1: δ31 P=+147,6 ppm; JPW=313 Hz M.+=595;2 δ3 p=+156 ppm JPW=304 Hz M.+=533; 90%dp) in two steps. Methyl lithium reacted with 1 to give stereospecific 3 (83%Yield) by P-O linkage (3 δ31 P=+64 ppm; JPW =261 Hz; M.+ ? 28=583). The aminophosphine complex 3 was stereochemically stable and was used for studies of synthetic applications. HCL gas reacted with 3 in CH2Cl2 to give the non optically active chlorophosphine complex 4 (δ31 P=+103,6 ppm; JPW=290 Hz; M.+ =482). This compound immediately gave salt 6 (δ31 P=+66,7 ppm; JPW =240 Hz) by reaction with (?)-menthol and triethylamine. The acid methanolysis of 3 gave a mixture of 5 and 6 and the unchanged (?)-ephedrine salt [5:30% yield; δ31 P=+114 ppm; Jpw=280 Hz; [α]D=+1,2° (CH2Cl2); M.+=478; 6 : 60% yield; δ31p=+102,9 ppm; JPW=264 Hz; [α]D =+16,9° (CH2Cl2); M.+=464]. Compound 6 was thus obtained with a 80% yield and a specific rotation of + 20,2° (CH2Cl2) in isopropanol/H2SO4 5M medium. The enantiomeric excess of 6 was determined by RMN31P. Acid hydrolysis of 3 or the reaction with CH3SO3H, gave phosphinous acid complex 6 with an optical rotation of + 4,8° or ?1,8° respectively. These results provide precious informations about the stereochemistry and reactivity of the P-N linkage in this aminophosphine transition metal series, which differs notably from that of the corresponding (PO) N bond. 相似文献
18.
Rustem Kamalov Grigory Stepanov Michael Pudovik Arkady Pudovik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Novel heterocyclic derivatives - 1,3,4-thiazaphospholines and 1,3,4-selenoazaphospolines 7, were obtained passing hydrogen sulfide or hydrogen selenide 2 through the solution of 0-phenylchloromethyl (chloro)thiophosphonate 1 and alkylthiocyanate followed by addition of triethylamine. It is assumed that 0-phenylchloromethylthiophosphonic and -selenophosphonic acids 3 are formed at the first stage, which further add to CN triple bond of alkylthiocyanates 4 to produce S- or Se-thiophosphonyldithio- or selenothioiminocarbonates 5. The latter undergo phosphorotropic rearrangement into appropriate S-thiophosphonyl dithio- or selenothiocarbamates 6. 相似文献
19.
A recent report about the synthesis of di and tri-substituted 2 (5H)-furanones starting from bromoaldehydes and potassium phenyl-acetate1 prompts us to report our own studies on the preparation of 3-aryl-5-arylmethylene-2 (5H)-furanones (or butenolides) 1. We have earlier reported2 a general method for the synthesis of 1 from phenylpropargyl aldehyde, 2 and arylacetic acids. Although several methods have been reported for the synthesis of the parent compound 1 (R = R1 = Ph)3–6, these methods have not been extended to other substituted furanones. Saikachi and Taniguchi7 prepared 1 (R = 5-nitro-2-thenyl, R1 = 2-thenyl and 2-furyl) in 16–17% yields. 相似文献
20.
James C. Goodwin 《Journal of carbohydrate chemistry》2013,32(2):255-263
Sodium bis(3-O-hydroxy-2-furyl methyl ketone) (3) and sodium 3-O-hydroxy-2-methyl-4-pyrone hydrate (4) were isolated and characterized from the interaction of isomaltol and maltol with sodium methoxide in boiling benzene (toluene or acetone). Elemental analyses of 3 furnished the formula C12H11NaO6, and this composition was confirmed by conversion to isomaltol O-benzoyl ester. 相似文献