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Woraluk Mansawat Chalothorn Boonlua Khatcharin Siriwong Tirayut Vilaivan 《Tetrahedron》2012,68(21):3988-3995
Pyrene as well as other aromatic hydrocarbons could be successfully incorporated into pyrrolidinyl peptide nucleic acid bearing a d-prolyl-2-aminocyclopentane carboxylic acid backbone (acpcPNA) as a base surrogate via a triazole linker employing Cu-catalyzed alkyne–azide cycloaddition (click chemistry). The labeling can be performed via a pre-clicked pyrene monomer or by post-synthetic modification of azide-containing acpcPNA on solid support. Thermal denaturation experiments suggested that the pyrene–triazole unit can behave as a universal base in the acpcPNA system. The mode of base-pairing has been proposed based on molecular dynamics simulations. Importantly, the fluorescence spectra of the pyrene-labeled single stranded acpcPNA and its hybrid with DNA are quite different. The ratio of emissions at 380 and 460 nm changed significantly (up to a factor of 7) upon hybrid formation with complementary DNA. 相似文献
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Using a designed control of conformations of tert-butylcalix[4]arene between cone and pinched cone, a highly selective receptor for small electron-deficient molecules with photoswitching binding ability was attained. [reaction: see text] 相似文献
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Woraluk Mansawat 《Tetrahedron letters》2007,48(24):4235-4238
Thiolated amino-alcohols have been synthesized and evaluated as a potential new class of chiral ligands for copper-catalyzed nitro-aldol reactions. The model nitro-aldol reaction took place smoothly at ambient temperature in the presence of catalytic amounts (5-15 mol %) of the ligands and copper(II) acetate to afford the nitro-aldol product in good to excellent yield without accompanying dehydration. Amino-alcohol ligands bearing N-(2-alkylthio)benzyl substituents provided only modest enantioselectivities (22-46% ee) while those carrying N-2-thienylmethyl substituents provided better enantioselectivities (up to 75% ee). A range of aromatic aldehydes were acceptable for the nitro-aldol reaction with nitromethane, giving moderate to good enantioselectivities (69-88% ee). 相似文献
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Vorawit Banphavichit Woraluk Mansawat Worawan Bhanthumnavin Tirayut Vilaivan 《Tetrahedron》2009,65(29-30):5849-5854
A practical procedure for catalytic asymmetric synthesis of optically active arylglycine derivatives via optically active α-aminonitriles has been developed. The N-benzhydryl α-arylaminonitrile intermediates were prepared in excellent yield (89–99%) and enantiomeric purity (96 to >98% ee) by enantioselective cyanation of aldimines with TMSCN/iPrOH in the presence of 2.5 mol % of an easily prepared Ti/chiral amino alcohol complex at 0 °C, without requiring slow addition of the cyanating agent. The easily racemized α-aminonitrile intermediates were efficiently hydrolyzed by an aqueous HCl/TFA mixture to give the arylglycine derivatives in good yield (60–92%) and moderate to excellent enantiomeric purity (85–98% ee). 相似文献
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The effect of ring size of four- to six-membered cyclic β-amino acid on the hybridization properties of pyrrolidinyl peptide nucleic acid with an alternating α/β peptide backbone is reported. The cyclobutane derivatives (acbcPNA) show the highest T(m) and excellent specificity with cDNA and RNA. 相似文献
7.
Worawan Bhanthumnavin Srinivasan Ganapathy Atta M. Arif Wesley G. Bentrude 《Heteroatom Chemistry》1998,9(2):155-160
Upon irradiation, 9-anthrylmethyl phosphite ( 2 ) undergoes the photo-Arbuzov rearrangement to give the corresponding phosphonate 3 . Prolonged irradiation led to the clean formation of the centrosymmetric, head to tail, [4 + 4] photocycloaddition product 4 as indicated by X-ray crystallographic analysis. The same photodimer results on irradiation of phosphonate 3 itself in solution or in the solid phase. Phosphite 2 does not undergo photodimerization to 6 . © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:155–160, 1998 相似文献
8.
An enantioselective Strecker synthesis employing novel chiral titanium complex catalysts derived from structurally simple chiral N-salicyl-β-amino alcohols is described. Reactions of N-benzylidenebenzylamine with trimethylsilyl cyanide in the presence of the catalyst (10 mol%) gave the corresponding α-aminonitrile in good to excellent yields, along with relatively high enantioselectivity (up to 86% ee). Similar reactions with various imines derived from aromatic aldehydes resulted in moderate to good enantioselectivity (44-81% ee). 相似文献
9.
The essentially stereochemically pure 1-arylethyl phosphorodiamidites 8 and 9 were irradiated by UV light in acetonitrile, benzene, and cyclohexane (Tables 1-4). Reaction via singlet free-radical pairs, formed by carbon-oxygen bond scission (Scheme 1), which are somewhat longer lived than those from the analogous phosphites 5 and 6, is proposed. Tetramethyl 1-phenylethylphosphorodiamidite (8) gives the photo-Arbuzov rearrangement product 10 in 59% +/- 2% GC yield, based on percent 8 consumed (Tables 1 and 4), along with the free radical dimerization product 2,3-diphenylbutane, 12a, in in amounts corresponding to ca. 19% of the potentially formed 1-phenylethyl radicals. Similarly, from 9, the photorearrangement product 11 is generated in 64 +/- 4% yield (Tables 2 and 4) along with a 18 +/- 2% accountability of the 1-naphthylethyl radicals as 12b. The photorearrangement of stereochemically enriched 8 (R/S = 99:1) gives 10 in which an apparent 67 +/- 2% (100y, eq 3, Table 4) of the initial radical pairs [3,14] recombine with retention of configuration at the stereogenic carbon (34 +/- 3% net retention, eq 5). With TEMPO present, 70% (100y, eq 3) of the initial 1-phenylethyl radicals, 14, from 8 combine with radicals 3 in the solvent cage with retained configuration at carbon (40% percent net retention, eq 5). The yield of product 10 is reduced to 54%, and 12a is absent. Similarly, the five-membered ring naphthylethyl analogue, phosphorodiamidite 9 (R/S = 98:2), affords largely (R)-11 with apparent 34 +/- 3% net retention. The degree of stereorandomization observed in these systems is higher than was reported previously for phosphites 5 and 6. The neglect of reconversion of pro-S 14 to pro-R 14 on the results of these studies is addressed. Estimated maximum values (eq 4) of kcomb/krot (2.3) for the proximate radical pairs [3,14] from 8 with TEMPO present appear to be at least 6-fold smaller than those of the analogous phosphite (R)-5 (average kcomb/krot = 13 with TEMPO present). Possible origins for this effect are proposed. 相似文献
10.
The direct UV irradiation of the 1-arylethyl phosphites 7, 8, and 9 was carried out in acetonitrile, benzene, and cyclohexane, as was the triphenylene-sensitized reaction of 9. Dimethyl 1-phenylethyl phosphite, 7, gives the photo-Arbuzov rearrangement product, dimethyl 1-phenylethylphosphonate (10), in 67% average yield and minor amounts (2%) of 2,3-diphenylbutane (11a) in quantum yields of 0.32 and 0.02, respectively. The photorearrangement of optically active, predominantly (R)-1-phenylethyl phosphite 7 (R/S = 97/3; 94% ee), at 35-40 degrees C proceeds with a high degree of stereospecificity at the stereogenic migratory carbon to give predominantly (R)-10 (R/S = 86/14, 72 +/- 2% ee). Use of the nitroxide radical trap TEMPO affords phosphonate 10, presumably all cage product, from predominantly (R)-7 (R/S = 97/3; 94% ee) in 64% yield (80% ee, R/S = 90/10). By contrast, the 1-(4-acetylphenyl)-ethyl phosphite, predominantly (S)-8 (S/R = 98/2, 96% ee), on direct irradiation gives the corresponding phosphonate (12) in only 20% yield along with dimer 11b in 40% accountability yield. Phosphonate 12 is nearly racemic (R/S = 52/48). Direct irradiation of predominantly (R)-9 (R/S = 98/2, 96% ee), a 1-(1-naphthyl)ethyl phosphite, results in a product distribution similar to that from predominantly (R)-7, but with a somewhat higher degree of retention of configuration in the product phosphonate 13 (R/S = 93/7, 86 +/- 3 ee). By contrast, the triplet triphenylene-sensitized photorearrangement of largely (R)-9 (R/S = 98/2, 96% ee) leads to product distributions similar to those from direct irradiation of predominantly (S)-8 and is accompanied by almost total loss of stereochemistry in its product phosphonate, 13 (R/S = 51/49). The partial loss of stereochemistry on direct irradiation of 7 and 9 provides evidence for radical pair formation. Furthermore, these stereochemical results are diagnostic of the multiplicity of the initial radical pair formed. Values for kcomb/krot for the proximate free radical pairs from 7 and 9, derived experimentally, are severalfold larger than those for the proximate singlet pair from Ph2C=C=N-CHPhMe, corrected to 35 degrees C. The possibility that kcomb is increased for the pairs from 7 and 9 is proposed. 相似文献