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Tomoyuki Manaka Shin‐Ichiro Nagayama Wannaporn Desadee Naoki Yajima Takuya Kumamoto Toshiko Watanabe Tsutomu Ishikawa Masatoshi Kawahata Kentaro Yamaguchi 《Helvetica chimica acta》2007,90(1):128-142
Nucleophilic ring‐opening reactions of 3‐aryl‐1‐benzylaziridine‐2‐carboxylates were examined by using O‐nucleophiles and aromatic C‐nucleophiles. The stereospecificity was found to depend on substrates and conditions used. Configuration inversion at C(3) was observed with O‐nucleophiles as a major reaction path in the ring‐opening reactions of aziridines carrying an electron‐poor aromatic moiety, whereas mixtures containing preferentially the syn‐diastereoisomer were generally obtained when electron‐rich aziridines were used (Tables 1–3). In the reactions of electron‐rich aziridines with C‐nucleophiles, SN2 reactions yielding anti‐type products were observed (Table 4). Reductive ring‐opening reaction by catalytic hydrogenation of (+)‐trans‐(2S,3R)‐3‐(1,3‐benzodioxol‐5‐yl)aziridine‐2‐carboxylate (+)‐trans‐ 3c afforded the corresponding α‐amino acid derivative, which was smoothly transformed into (+)‐tert‐butyl [(1R)‐2‐(1,3‐benzodioxol‐5‐yl)‐1‐methylethyl]carbamate((+)‐ 14 ) with high retention of optical purity (Scheme 6). 相似文献
2.
Summary Polymer-supported and polymeric chiral guanidines carrying an imidazolidine skeleton are designed as polymer-based base catalysts.
Thus, (R)-2-[(S)-1-hydroxymethyl-2-phenylethylimino]-4-phenylimidazolidine was newly prepared from (R)-phenylglycine as the key functional unit of these guanidines. Application of the polymer-based chiral guanidines to the
asymmetric Michael reaction of t-butyl diphenyliminoacetate with MVK led to expected asymmetric induction in the Michael adduct with moderate enantioselectivity
in the use of the latter polymeric chiral guanidines. 相似文献
3.
We successfully isolated a spiro imidazolidine-oxazolidine intermediate in the reaction of guanidinium ylide mediated aziridination using alpha-bromocinnamaldehyde. X-ray crystallographic analysis unambiguously revealed that the stereogenic centers of the spiro intermediate were in a trans configuration. The role of the spiro compound as an intermediate in the aziridination reaction was confirmed by observation of its smooth chemical conversion into aziridine products. 相似文献
4.
Single step formulas and multi-step formulas of the integration method for solving the initial value problem of ordinary differential equation 总被引:1,自引:0,他引:1
Maitree Podisuk Ungsana Chundang Wannaporn Sanprasert 《Applied mathematics and computation》2007,190(2):1438-1444
Adam–Bashforth method and Adam–Moulton method are two known multi-step methods for finding the numerical solution of the initial value problem of ordinary differential equation. These two methods used the Newton backward difference method to approximate the value of f(x,y) in the integral equation which is equivalent to the given differential equation. 相似文献
5.
Sahakitpichan P Disadee W Ruchirawat S Kanchanapoom T 《Chemical & pharmaceutical bulletin》2011,59(9):1160-1162
A new 3-hydroxydihydrobenzofuran glucoside, gnaphaliol 9-O-β-D-glucopyranoside (2), was isolated from the aerial parts of Gnaphalium polycaulon together with 1-{(2R*,3S*-3-(β-D-glucopyranosyloxy)-2,3-dihydro-2-[1-(hydroxyl methyl)vinyl]-1-benzofuran-5-yl}-ethanone or gnaphaliol 3-O-β-D-glucopyranoside (1), (Z)-3-hexenyl O-β-D-glucopyranoside (3) and adenosine (4). The absolute configurations at C-2 and C-3 positions of compound 1 were determined to be 2R and 3R. The structures of these compounds were elucidated on the basis of their physical and spectroscopic data. 相似文献
6.
Wannaporn Disadee Poonsakdi Ploypradith Thammarat AreeNarongsak Chaichit Somsak Ruchirawat 《Tetrahedron letters》2011,52(46):6142-6144
A novel approach for the syntheses of lophocladines A and B has been developed. These compounds were prepared in 4-6 steps with moderate to excellent overall yields. The key step involved the nucleophilic substitution of 4-chloronicotinic acid with the carbanion generated from phenylacetonitrile. Subsequent reduction of the cyano group, lactamization and oxidation furnished lophocladine A in 50% yield over 4 steps. Further amination with various amines led to lophocladine B and its C1 analogues in good yields. In addition, the synthesized compounds were evaluated for their cytotoxicity against leukaemia cells. 相似文献
7.
[Reaction: see text]. Reaction of chiral guanidinium ylides with alpha,beta-unsaturated aldehydes gives 3-(alpha,beta-unsaturated) aziridine-2-carboxylates in high diastereo- and enantioselectivities (up to 93% diastereomeric excess and 98% enantiomeric excess). 3-(1-methylvinyl)- and 3-[(E)-pentadec-1-enyl]aziridine-2-carboxylates were successfully employed to prepare (2R,3S)-3-hydroxyleucinate and d-erythro-sphingosine, respectively. 相似文献
8.
Shikii K Seki H Yamaguchi K Disadee W Watanabe T Ishikawa T 《Chemical & pharmaceutical bulletin》2004,52(7):864-865
Polymer-supported (PS) reagents can be easily characterized using a cross polarization magic angle spinning method in solid state (13)C-NMR. The technique was applied to the characterization of PS-dimethylimidazolidinone, analogue to potential heterogeneous dehydrating agent. 相似文献
9.
Wannaporn DisadeeChulabhorn Mahidol Poolsak SahakitpichanSomkit Sitthimonchai Somsak Ruchirawat Tripetch Kanchanapoom 《Tetrahedron》2011,67(23):4221-4226
Six new flavonol 3-O-robinobiosides and 3-O-(2″-O-α-l-rhamnopyranosyl)-robinobiosides, sesuviosides A-F, were isolated from the aerial portion of Sesuvium portulacastrum together with ecdysterone, adenosine, 2′-O-methyladenosine, and l-tryptophan. The structure elucidations were based on analyses of chemical and spectroscopic data including 1D and 2D-NMR. Sesuviosides A-F and their aglycones exhibited radical scavenging activity using DPPH and ORAC assays. 相似文献
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