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1.
β-Keto-β-sulfonylenamines 2a,b reacted with benzamidine or guanidines to give 2,4-disubstituted 5-methanesulfonylpyrimidines 3a-d , whose methanesulfonyl groups were substituted by n-butyllithium or alkylmagnesium bromides to yield 2,4-disubstitued 5-alkylpyrimidines 6a-d. 2-Substituted 4-amino-5-sulfonylpyrimidines 7a,b, 8 and 2-substituted 5-benzenesulfonylpyrimidin-4-ones 9a,b were similarly obtained from β-cyano-β-sulfonylenamines 2c,d and β-ethoxycarbonyl-β-sulfonylenamine ( 2e ), respectively. 相似文献
2.
A. Lffler F. Norris W. Taub K. L. Svanholt A. S. Dreiding 《Helvetica chimica acta》1970,53(2):403-417
By heating with iron powder at 120–150° some γ-bromo-α, β-unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ7alpha;-butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ-bromocrotonate ( 1c ) and the corresponding acid ( 1d ) to Δα-butenolide ( 8a ), methyl γ-bromotiglate ( 3c ) and the corresponding acid ( 3d ) to α-methyl-Δα-butenolide ( 8b ), a mixture of methyl trans- and cis-γ-bromosenecioate ( 7c and 7e ) and a mixture of the corresponding acids ( 7d and 7f ) to β-methyl-Δα-butenolide ( 8c ). The procedure did not work with methyl trans-γ-bromo-Δα-pentenoate ( 5c ) nor with its acid ( 5d ). Most of the γ-bromo-α, β-unsaturated carboxylic esters ( 1c, 7c, 7e and 5c ) are available by direct N-bromosuccinimide bromination of the α, β-unsaturated esters 1a, 7a and 5a ; methyl γ-bromotiglate ( 3c ) is obtained from both methyl tiglate ( 3a ) and methyl angelate ( 4a ), but has to be separated from a structural isomer. The γ-bromo-α, β-unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β-unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine-carrying carbon anti to the carboxylic ester group; an exception is methyl γ-bromo-senecioate, for which the two isomers (cis, 7e , and trans, 7d ) have about the same stability. The N-bromosuccinimide bromination of the α,β-unsaturated carboxylic acids 1b , 3b , 4b , 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ-bromocrotonic acid ( 1 d ), γ-bromotiglic acid ( 3 d ), trans- and cis-γ-bromosenecioic acid ( 7d and 7f ) as well as trans-γ-bromo-Δα-pentenoic acid ( 5d ) have been prepared. Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond. α-Methyl-Δα-butenolide ( 8b ) was converted to 1-benzyl-( 9a ), 1-cyclohexyl-( 9b ), and 1-(4′-picoly1)-3-methyl-Δα-pyrrolin-2-one ( 9 c ) by heating at 180° with benzylamine, cyclohexylamine, and 4-picolylamine. The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity. 相似文献
3.
Bernhard Krutler Christian Caderas Robert Konrat Michael Puchberger Christoph Kratky 《Helvetica chimica acta》1995,78(3):581-599
The four α,α,α, β,β,β,-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates 2b, d–f , with a free b-, d-, e-, and f-propionic-acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ-dicyanocobyrinate (cobester; 1 ) in aqueous sulfuric acid. The cobester monoacids 2b, d–f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic-acid function was determined by an extensive analysis of 2b, d–f using 2D-NMR techniques; an analysis of the C,H-coupling network topology resulted in an alternative assignment strategy for cobyrinic-acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b-isomer 2b , was also obtained in the solid state from a single-crystal X-ray analysis. Earlier structural assignments based on 1D-NMR spectra of the corresponding regioisomeric monoamides 3b, d–f (obtained from crystalline samples of the monoacids 2b, d–f ) were confirmed by the present investigations. 相似文献
4.
Synthesis of (R)-β, β-Caroten-2-ol and (2R, 2′R)-β, β-Carotene-2,2′-diol Starting from geraniol, the two carotenoids (R)-β, β-caroten-2-ol ( 1 ) and (2R, 2′R)-β, β-carotene-2,2′-diol ( 3 ) were synthesized. The optically active cyclic building block was obtained by an acid-catalysed cyclisation of the epoxide (R)- 4 . The enantiomeric excess of the product was > 95 %. 相似文献
5.
Fakhry Abdel-Aziz El-Bassiouny 《中国化学》1991,9(4):360-364
α- and β-Acetylnaphthalenes condensed with dimethyl β,β-dimethyl glutarate in the presence of sodium hydride to give the corresponding half-esters, the E-isomers 2a and 2b being predominant. The structure and configuration of the half-esters were characterized by chemical and spectroscopic means. 相似文献
6.
Synthesis of Diastereo- and Enantioselectively Deuterated β,ε-, β,β-, β,γ- and γ,γ-Carotenes We describe the synthesis of (1′R, 6′S)-[16′, 16′, 16′-2H3]-β, εcarotene, (1R, 1′R)-[16, 16, 16, 16′, 16′, 16′-2H6]-β, β-carotene, (1′R, 6′S)-[16′, 16′, 16′-2H3]-γ, γ-carotene and (1R, 1′R, 6S, 6′S)-[16, 16, 16, 16′, 16′, 16′-2H6]-γ, γ-carotene by a multistep degradation of (4R, 5S, 10S)-[18, 18, 18-2H3]-didehydroabietane to optically active deuterated β-, ε- and γ-C11-endgroups and subsequent building up according to schemes \documentclass{article}\pagestyle{empty}\begin{document}${\rm C}_{11} \to {\rm C}_{14}^{C_{\mathop {26}\limits_ \to }} \to {\rm C}_{40} $\end{document} and C11 → C14; C14+C12+C14→C40. NMR.- and chiroptical data allow the identification of the geminal methyl groups in all these compounds. The optical activity of all-(E)-[2H6]-β,β-carotene, which is solely due to the isotopically different substituent not directly attached to the chiral centres, is demonstrated by a significant CD.-effect at low temperature. Therefore, if an enzymatic cyclization of [17, 17, 17, 17′, 17′, 17′-2H6]lycopine can be achieved, the steric course of the cyclization step would be derivable from NMR.- and CD.-spectra with very small samples of the isolated cyclic carotenes. A general scheme for the possible course of the cyclization steps is presented. 相似文献
7.
2-Alkoxy-4-heteroarylaminomethylene-5(4H)-thiazolones 4 were converted with various nucleophiles into β-heteroarylamino-α,β-dehydro-α-amino acid derivatives 11, 14, 15, 16, 17, 18 , and 19 . Reduction of 4 with sodium borohydride in ethanol saturated with gaseous ammonia afforded the corresponding β-heteroaryl-amino substituted alanyl amides 20 . Thiazoledione derivative 7a was transformed with sodium methoxide in methanol into 1-(4,6-dimethylpyrimidinyl-2)-4-mercaptocarbonylimidazol-2(3H)-one ( 8a ). 相似文献
8.
N-Fmoc-Protected (Fmoc = (9H-fluoren-9-ylmethoxy)carbonyl) β-amino acids are required for an efficient synthesis of β-oligopeptides on solid support. Enantiomerically pure Fmoc-β3-amino acids β3: side chain and NH2 at C(3)(= C(β)) were prepared from Fmoc-protected (S)- and (R)-α-amino acids with aliphatic, aromatic, and functionalized side chains, using the standard or an optimized Arndt-Eistert reaction sequence. Fmoc-β2- Amino acids (β2 side chain at C(2), NH2 at C(3)(= C(β))) configuration bearing the side chain of Ala, Val, Leu, and Phe were synthesized via the Evans' chiral auxiliary methodology. The target β3-heptapeptides 5–8 , a β3- pentadecapeptide 9 and a β2-heptapeptide 10 were synthesized on a manual solid-phase synthesis apparatus using conventional solid-phase peptide synthesis procedures (Scheme 3). In the case of β3-peptides, two methods were used to anchor the first β-amino acid: esterification of the ortho-chlorotrityl chloride resin with the first Fmoc-β-amino acid 2 (Method I, Scheme 2) or acylation of the 4-(benzyloxy)benzyl alcohol resin (Wang resin) with the ketene intermediates from the Wolff rearrangement of amino-acid-derived diazo ketone 1 (Method II, Scheme 2). The former technique provided better results, as exemplified by the synthesis of the heptapeptides 5 and 6 (Table 2). The intermediate from the Wolff rearrangement of diazo ketones 1 was also used for sequential peptide-bond formation on solid support (synthesis of the tetrapeptides 11 and 12 ). The CD spectra of the β2- and β3-peptides 5 , 9 , and 10 show the typical pattern previously assigned to an (M) 31 helical secondary structure (Fig.). The most intense CD absorption was observed with the pentadecapeptide 9 (strong broad negative Cotton effect at ca. 213 nm); compared to the analogous heptapeptide 5 , this corresponds to a 2.5 fold increase in the molar ellipticity per residue! 相似文献
9.
Claudete J. Valduga Hugo S. Braibante Mara E. F. Braibante 《Journal of heterocyclic chemistry》1997,34(5):1453-1457
The reactivity of the β-enamino ketones, 3-amino-1-(p-phenyl-substituted)-2-buten-1-ones 1a-d and β-enamino esters, ethyl 3-amino-3-(p-phenyl-substituted)-2-propenoates 5a-d was systematically studied when allowed to react with hydrazine and methylhydrazine under solid support K -10/ultrasound conditions and in homogeneous media (reflux in ethanol or dichloromethane). The products were pyrazoles 2a-d , N-methylpyrazoles 3a-d, 4a-d and N-methylpyrazolinones 6a-c and 7a-c . The regiochemistry of the cyclization reactions showed dependence upon the reaction conditions employed as well as upon the sub-stituent in the aromatic ring. 相似文献
10.
Carotenoid Glycosyl Esters Synthesis of β-D -Glucosyl 8′-Apo-β-carotene-8′-oate and β-D -Glucosyl Vitamin-A-oate (β-D -Glucosyl Retionate) β-D -glucosyl 8′-apo-β-carotene-8′-oate (III) and β-D -glucosyl vitamin-A-oate (VI) were regio- and stereoselectively synthesized in high yields from the N-acylimidazoles I and IV, respectively, or from the N-acyltriazoles II and V, respectively, and unprotected β-D -glucose, according to the method described for the synthesis of di(β-D -glucosyl) 8,8′-diapo-carotene-8,8′-dioate [1]. It seems that this method can generally be applied for the synthesis of β-D -glucosyl esters of polyene carboxylic acids. 相似文献
11.
Claudete J. Valduga Hugo S. Braibante Mara E. F. Braibante 《Journal of heterocyclic chemistry》1998,35(1):189-192
The reactivity of the β-enamino ketones, 3-amino-1-(p-phenyl-substituted)-2-buten-1-ones 1a-d and β-enamino esters. Ethyl-3-amino-3-(p-phenyl-substituted)-2-propenoates 5a-d were evaluated by systematic studies of the reactions with hydrazine and methylhydrazine by reactions with solid support K-10/ultrasound and homogeneous media (reflux in ethanol or dichloromethane) yielding pyrazole rings 2a-d , N-methylpyrazoles 3a-d, 4a-d and N-methylpyrazolinones 6a-c and 7a-c . The regiochemistry of the cyclization showed dependence of the reaction conditions employed as well as the substituent in the aromatic ring. 相似文献
12.
Hans Zimmer Adel Amer Douglas Ho R. Palmer-Sungail 《Journal of heterocyclic chemistry》1991,28(6):1501-1510
The reaction pathway of 4-aroyl-3-hydroxy-2(5H)-furanones 1 with diamines depends on the nature of the amine as well as on the applied reaction conditions. Thus, the reaction of 1a-d with 5,6-diamino-1,3-dimethyluracil 5 led to the formation of two isomeric Schiff bases 7a-d and 8a-d . Conversely type 1 compounds reacted with 4,5-diaminopyrimidine 9 or 2,3-diaminopyridine 10 to form the mono acid-base adducts 11a and 11b respectively. When type 1 compounds were reacted with aliphatic diamines 13a-d or p-phenylenediamine and p-xylenediamine, respectively also an immediate formation of acid-base adducts 15a-f was observed. The reaction of a number of O-methylated type 1 compounds with 1,2-ethylenediamine afforded the novel seven-membered ring compounds 18a-d in good yields. The analogous reaction of O-alkylated 1a with o-phenylenediamine 2 or 2,3-diaminonaphthalene gave the expected tricyclic ring systems 19 or 20 . 相似文献
13.
Two types of endocyclic enol-acetal forming β-elimination were investigated on synthetic model compounds. In both types the 4-O-methanesulfonyl residue was chosen as leaving group. The a,e-β-elimination was proved on 2,3-benzyl ether protected D -glucopyranosiduronate derivatives I, and the a, a-β-elimination on the analogous substituted D -galactopyranosiduronates XVII. Using a small excess of KOH in methanol at 25°, a quick elimination of a molecule of methanesulfonic acid was observed, and as reaction product the 4,5-unsaturated 4-deoxyhexopyranosiduronate derivative II was obtained. Only an unimportant stereoselectivity was found between the a,e- and a,a-mesylate β-eliminations. The 4,5-unsaturated 4-deoxyhexopyranosiduronates show a strong UV. maximum at 238 nm, and Cotton effects in the ORD. spectra. This stable ring system with an endocyclic enol-acetal linkage is present in a half-chair (H) conformation. The structure of the unsaturated deoxyhexopyranosiduronate obtained was established by structure- and stereo-correlation with a 2-deoxy-L -xylose derivative, showing that a ring contraction during the β-elimination does not occur. 相似文献
14.
Jurij Svete Branko Stanovnik Miha Tiler Ljubo Goli
Ivan Leban 《Journal of heterocyclic chemistry》1989,26(1):145-153
From heteroarylaminomethyleneoxazolones 4 , obtained from N-heteroarylformamidines 2 and 2-phenyl-5-oxo-4,5-dihydro-1,3-oxazole ( 3 ), the following β-heteroarylamino-α,β-dehydro-α-amino acid derivatives were prepared: methyl 8 and ethyl esters 9 , amides 10 and 11 , hydrazides 12 , and azides 15 . By catalytic hydrogenation the compounds 4 were converted into β-heteroarylamino substituted amides 18 and β-heteroarylamino-α-amino acids 20 . 相似文献
15.
Wolfgang Kreiser Voker Rüschenbaum Hans Bauer Joachim Buddrus 《Helvetica chimica acta》1984,67(8):2231-2235
Skeleton Rearrangement of an α-β-Unsaturated γ,δ-Epoxyketone during Birch Reduction: Structure Elucidation by Means of 13C-INADEQUATE-NMR Spectroscopy When the γ-epoxide 2 of β-ionone is treated under standard Birch-reduction conditions, unexpectedly a 70% combined yield of regioisomeric octalones 4 and 5 is isolated. These products unquestionably result form cleavage of the central epoxide C?C bond. The structure of compounds 4 and 5 could be determined by means of 13C-INADEQUATE-NMR spectroscopy. 相似文献
16.
Dieter Seebach Paola E. Ciceri Mark Overhand Bernhard Jaun Dario Rigo Lukas Oberer Ulrich Hommel Ren Amstutz Hans Widmer 《Helvetica chimica acta》1996,79(8):2043-2066
Structural prerequisites for the stability of the 31 helix of β-peptides can be defined from inspection of models (Figs. 1 and 2): lateral non-H-substituents in 2- and 3-position on the 3-amino-acid residues of the helix are allowed, axial ones are forbidden. To be able to test this prediction, we synthesized a series of heptapeptide derivatives Boc-(β-HVal-β-HAla-β-HLeu-Xaa-β-HVal-β-HAla-β-HLeu)-OMe 13–22 (Xaa = α- or β-amino-acid residue) and a β-depsipeptide 25 with a central (S)-3-hydroxybutanoic-acid residue (Xaa = –OCH(Me)CH2C(O)–) (Schemes 1 3). Detailed NMR analysis (DQF-COSY, HSQC, HMBC, ROESY, and TOCSY experiments) in methanol solution of the β-hexapeptide H(-β-HVal-β-HAla-β-HLeu)2-OH ( 1 ) and of the β-heptapeptide H-β-HVal-β-HAla-β-HLeu-(S,S)-β-HAla(αMe)-β-HVal-β-HAla- β-HLeu-OH ( 22 ), with a central (2S,3S)-3-amino-2-methylbutanoic-acid residue, confirm the helical structure of such β-peptides (previously discovered in pyridine solution) (Fig.3 and Tables 1–5). The CD spectra of helical β-peptides, the residues of which were prepared by (retentive) Arndt-Eistert homologation of the (S)- or L -α-amino acids, show a trough at 215 nm. Thus, this characteristic pattern of the CD spectra was taken as an indicator for the presence of a helix in methanol solutions of compounds 13–22 and 25 (including partially and fully deprotected forms) (Figs.4–6). The results fully confirm predicted structural effects: incorporation of a single ‘wrong’ residue ((R)-β-HAla, β-HAib, (R,S)-β-HAla(α Me), or N-Me-β-HAla) in the central position of the β-heptapeptide derivatives A (see 17, 18, 20 , or 21 , resp.) causes the CD minimum to disappear. Also, the β-heptadepsipetide 25 (missing H-bond) and the β-heptapeptide analogs with a single α-amino-acid moiety in the middle ( 13 and 14 ) are not helical, according to this analysis. An interesting case is the heptapeptide 15 with the central achiral, unsubstituted 3-aminopropanoic-acid moiety: helical conformation appears to depend upon the presence or absence of terminal protection and upon the solvent (MeOH vs. MeOH/H2O). 相似文献
17.
Transformations of N'-heteroaryl-N,N-dimethylformamidines 1 as a general method for the preparation of β-heteroarylamino-α,β-dehydro-α-amino acids, β-heteroarylamino-α-amino acid derivatives 5–9 , and dipeptides 10 , are described. 相似文献
18.
α,β-Doubly deprotonated nitroalkanes: Super-enamines? At temperatures between ?90° and ?78° both the α and β-proton of 1-aryl-2-nitro-ethanes ( 1 ) are abstracted by n-butyllithium to give the dilithio derivatives of 3 . These turn out to be excellent nucleophiles combining with alkyl halides, aldehydes, ketones, and ω-nitro styrenes at the β-nitro carbon atom to give products of type 2 . It is shown that 2-nitro-propane undergoes the same double deprotonation and can be coupled with benzaldehyde at one of the β-nitro carbon atoms to yield 4 . It is proposed to consider the new reagents as super-enamines 3c . 相似文献
19.
Synthesis of Macrocyclic α,β-Unsaturated γ-Oxolactones by Ring-Enlargement Reactions; a New Path to the Macrocyclic Lactone Antibiotic A 26771 B A new synthetic route to the α,β-unsaturated γ-oxolactones 2a and 2b , involving two ring-enlarement reactions, is described. Ring opening of bicyclic α-nitroketones of the type 3 gave ring-enlarged compounds of the type 4 which were converted to monoprotected diketones of the type 10 by using a variation of the Nef reaction as a key step. Macrocyclic lactones of the type 11 were obtained by Baeyer-Villiger oxidation and converted into compounds of the type 2 . The conversion of 2b to the macrocyclic lactone antibiotic A 26771 B ( 1 ) is already described in the literature. 相似文献
20.
Isozeaxanthin: Chirality and Enantioselective Synthesis of (4R,4′R)-Isozeaxanthin ((?)-(4R,4′R)-β, β-Carotin-4,4′-diol) The absolute configuration of optically active isozeaxanthin was established by synthesis using (?)-(R)-4-hydroxy-β-ionon ( 2 ) [18] as starting material. 相似文献