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1.
A simple synthesis of furo[2,3-c]pyridine and its 2- and 3-methyl derivatives from ethyl 3-hydroxyisonicotinate ( 2 ) is described. The hydroxy ester 2 was O-alkylated with ethyl bromoacetate or ethyl 2-bromopropionate to give the diester 3a or 3b . Cyclization of compound 3a afforded ethyl 3-hydroxyfuro [2,3-c]pyridine-2-carboxylate ( 4 ) which was hydrolyzed and decarboxylated to give furo[2,3-c]pyridin-3(2H)-one ( 5a ). Cyclization of 3b gave the 2-methyl derivative 5b . Reduction of 5a and 5b with sodium borohydride yielded the corresponding hydroxy derivative 6a and 6b , respectively, which were dehydrated with phosphoric acid to give furo[2,3-c]pyridine ( 7a ) and its 2-methyl derivative 7b . 4-Acetylpyridin-3-ol ( 8 ) was O-alkylated with ethyl bromoacetate to give ethyl 2-(4-acetyl-3-pyridyloxy) acetate ( 9 ). Saponification of compound 9 , and the subsequent intramolecular Perkin reaction gave 3-methylfuro[2,3-c]pyridine ( 10 ). Cyclization of 9 with sodium ethoxide gave 3-methylfuro[2,3-c]pyridine-2-carboxylic acid, which in turn was decarboxylated to give compound 10 . 相似文献
2.
A New Synthesis of (±)-Dihydrorecifeiolide Ethyl 1-(2′-formylethyl)-2-oxocyclooctane-1-carboxylate ( 2 ) prepared by Michael reaction of ethyl 2-oxocyclooctane-1-carboxylate ( 1 ) was regioselectively methylated at the aldehyde group with (CH3)2Ti[OCH(CH3)2]2 to give 3 (Scheme 1). The alcohol 3 was treated with Bu4NF to give the deethoxycarbonylated product 4 which by distillation gave the bicyclic enol ether 5 . Oxidation (m-chloroperbenzoic acid) of 5 and reduction of the resulting oxolacton 6 yielded the title compound (±)-dihydrorecifeiolide ( 7 ) in an overall yield of nearly 50 %. Methylation of the aldehyde 2 with MeLi gave the ring-enlarged lacton 9 in poor yield (13 %). The deethoxycarbonylation reaction 3 → 4 was studied in more detail (Scheme 3). 相似文献
3.
α-(Aminomethylene)-9-(methoxymethyl)-9H-purine-6-acetamide and the ethyl acetate, 3 and 8 , have been synthesized by catalytic hydrogenation of 6-cyanomethylene-9-methoxymethylpurine derivatives 2 and 7 which were obtained by the substitution of 6-chloro-9-(methoxymethyl)purine ( 1 ) with α-cyanoacetamide and ethyl cyanoacetate, respectively. Substitution of 3 and 8 with amines gave the corresponding N-substituted α-(aminomethylene)-9-(methoxymethyl)-9H-purine-6-acetamide and the ethyl acetate 4 and 10 . Reaction of 3 with piperidine gave 9-(methoxymethyl)-9H-purine-6-acetamide ( 5 ). 相似文献
4.
Timothy A. Riley William J. Hennen N. Kent Dalley Bruce E. Wilson Roland K. Robins Steven B. Larson 《Journal of heterocyclic chemistry》1987,24(4):955-964
A new C-glycosyl precursor for C-nucleoside synthesis, 2,5-anhydroallonamidine hydrochloride ( 4 ) was prepared and utilized in a Traube type synthesis to prepare 2-(β-D-ribofuranosyl)pyrimidines, a new class of C-nucleosides. The anomeric configuration of 4 was confirmed by single-crystal X-ray analysis. Reaction of 4 with ethyl acetoacetate gave 6-methyl-2-(β-D-ribofuranosyl)pyrimidin-4-(1H)-one ( 5 ). Reaction of 4 with diethyl sodio oxaloacetate gave 2-(β-D-ribofuranosyl)pyrimidin-6(1H)-oxo-4-carboxylic acid ( 6 ). Esterification of 6 with ethanolic hydrogen-chloride gave the corresponding ester 7 which when treated with ethanolic ammonia gave 2-(β-D-ribofuranosyl)pyrimidin-6(1H)-oxo-4-carboxamide ( 8 ). Condensation of 2,5-anhydroallonamidine hydrochloride ( 4 ) with ethyl 4-(dimethylamino)-2-oxo-3-butenoate ( 9 ), gave ethyl 2-(β-D-ribofuranosyl)pyrimidine-4-carboxylate ( 10 ). Treatment of 10 with ethanolic ammonia gave 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamide ( 11 ). Single-crystal X-ray analysis confirmed the β-anomeric configuration of 11. Acetylation of 11 followed by treatment with phosphorus pentasulfide and subsequent deprotection with sodium methoxide gave 2-(β-D-ribofuranosyl)pyrimidine-4-thiocarboxamide ( 14 ). Dehydration of the acetylated amide 12 with phosphorous oxychloride provided 2-(β-D-ribofuranosyl)pyrimidine-4-carbonitrile ( 15 ). Treatment of 15 with sodium ethoxide gave ethyl 2-(β-D-ribofuranosyl)pyrimidine-4-carboximidate ( 16 ), which was converted to 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamidine hydrochloride ( 17 ) by treatment with ethanolic ammonia and ammonium chloride. Treatment of 16 with hydroxylamine yielded 2-(β-D-ribofuranosyl)pyrimidine-4-N-hydroxycarboxamidine ( 18 ). Treatment of 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamide ( 11 ) with phosphorus oxychloride gave the corresponding 5′-phosphate, 19 , Coupling of 19 with AMP using the carbonyldiimidazole activation procedure gave the corresponding NAD analog, 2-(β-D-ribofuranosyl)pyrimidine-4-carboxamide-(5′ ? 5′)-adenosine pyrophosphate ( 20 ). 相似文献
5.
Ho Sik Kim Tong Eun Kim Seong Uk Lee Dong Il Kim Sung Wook Han Yoshihisa Okamoto Takako Mitomi Yoshihisa Kurasawa 《Journal of heterocyclic chemistry》1998,35(6):1515-1520
The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 5 with a 2-fold molar amount of ethyl chloroglyoxalate gave ethyl 8-chloro-4-methyl-4H-1,3,4-oxadiazino[5,6-b]quinoxaline-2-carboxylate 6 , whose reaction with hydrazine hydrate afforded the C2-hydrazinocarbonyl derivative 7 . The reaction of compound 7 with nitrous acid provided the C2-acylazide derivative 8 , which was converted into the C2-amino 9 , C2-carbamate 11a-c, 12a,b , and C2-ureido 13a-c, 14 derivatives. The mass spectral fragmentation patterns were examined for compounds 10–14 , wherein the molecular ion peak did not appear in the mass spectra of compounds 10c, 11a-c, 12a,b, 13c , and 14. 相似文献
6.
The reaction of 5a-acetyl-6-ethoxycarbonyl-5a,6a-dihydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine-3-carbonitrile ( 1a ) with benzylamine gave ethyl l-benzyl-5-cyano-8a,9-dihydro-2-methyl-1H-pyrrolo[3,4-e]-pyrazolo[1,5-a]pyrimidine-8a-carboxylate ( 2a ), in addition to 5-acetyl-3-benzylamino-1-(4-cyanopyrazol-3-yl)- 2-pyridone ( 3 ). Reaction of 1a with aniline gave ethyl 6-acetyl-8-anilino-3-cyano-7,8-dihydro-4H-pyrazolo-[1,5-a][1,3]diazepine-8-carboxylate ( 4 ), in addition to ethyl 3-cyano-7-methyl-6-pyrazolo[1,5-a]pyrimidine-acrylate ( 5 ). On the other hand, the same reactions of 1b with benzylamine or aniline gave 2b or 8b , respectively. Though catalytic hydrogenation of 1a over 5% palladium-carbon proceeded by ring fission of cyclopropane ring to give 9 , 1a (or 1b ) afforded 4,5-dihydro derivatives ( 13 or 15 ) by catalytic hydrogenation over platinum oxide. The reactivity of 5-methoxy-4,5,5a,6a-tetrahydro-6H-cyclopropa[e]pyrazolo[1,5-a]pyrimidine ( 16 ), which are related analogs of 1a,b , is also described. 相似文献
7.
Diethyl [2-(3- or 4-pyridinyl)-4-pyrimidinyl]aminomethylenemalonates 5 prepared by the reaction between 2-(3- or 4-pyridinyl)-4-pyrimidinamines 3 and diethyl ethoxymethylenemalonate ( 4 ) were thermally cyclized to afford ethyl 5,8-dihydro-5-oxo-2-(3- or 4-pyridinyl)pyrido[2,3-d]pyrimidine-6-carboxylates 6 . The later were alkylated with ethyl iodide and then saponified to give 5,8-dihydro-8-ethyl-5-oxo-2-(3- or 4-pyridinyl)pyrido-[2,3-d]pyrimidine-6-carboxylic acids 2 . Thermal cyclization of diethyl (2-hydroxy-4-pyrimidinyl)amino-methylenemalonate ( 8 ) gave ethyl 1,6-dihydro-4,6-dioxo-4H-pyrimido[1,6-a]pyrimidine-3-carboxylate ( 10 ) instead of ethyl 5,8-dihydro-2-hydroxy-5-oxopyrido[2,3-d]pyrimidine-6-carboxylate ( 9 ) as previously claimed. 相似文献
8.
A method for the synthesis of the title compound 3 consisted of an intramolecular cyclization in a stannic chloride catalyzed Friedel-Crafts reaction of N-(2-methylthiophenyl)-5-oxoproline chloride 10 , prepared by chlorination of the corresponding acid 9 obtained by hydrolysis of its ethyl ester 8 . Condensation of 2-methylthioaniline 4 with diethyl bromomalonate 5 afforded diethyl 2-methylthioanilinomalonate 6 which gave 8 either directly by reaction with ethyl acrylate or by alkylation with ethyl β-bromopropionate or ethyl acrylate and cyclization of resulting triethyl 2-(2-methylthio)anilino-2-carboxyglutarate 7 . This method was not convenient because of the poor yield of 3 (14%). On the other hand, cyclization of N-(2-mercaptophenyl)-5-oxoproline 14 with DCC and DMAP provided 3 in 45% yield. Oxidation with m-CPBA of the esters 11 and 8 , demethylation via the Pummerer rearrangement of the respective sulphoxides 12 and 17 with TFAA and oxidation with iodine of resulting N-(2-mercap-tophenyl)-5-oxoproline esters 13 and 18 gave the corresponding disulphides 16 and 19 . Hydrolysis of these latter compounds and reduction of the resulting bis[2-[2-(hydroxycarbonyl)-5-oxo-1-pyrrolidinyl]phenyl] disulphide 15 with sodium dithionite afforded the required 14 . Deprotection of t-butyl ester 13 with TFA at 55° to obtain 14 led to 3 in 42% yield. Finally the Pummerer rearrangement of N-(2-methylsulphinylphenyl)-5-oxo-proline 20 yielded the mixture of 14 and 15 . 相似文献
9.
Akira Hasegawa Takashi Ando Akihiko Kameyama Makoto Kiso 《Journal of carbohydrate chemistry》2013,32(5):645-658
Abstract Stereocontrolled synthesis of sialyl Lex epitope and its ceramide derivative with regard to the introduction of galactose or β-D-galactosyl ceramide into the terminal N-acetylglucosamine residue of sialyl Lex determinant is described. Königs-Knorr condensation of 2-(trimethylsilyl)ethyl 2, 4, 6-tri-O-benzyl-β-D-galactopyranoside (4) with 3, 4, 6-tri-O-acetyl-2-deoxy-2-phthalimido-D-glucopyranosyl bromide (5) gave the desired β-glycoside 6, which was converted into 2-(trimethylsilyl)ethyl O-(2-acetamido-4, 6-O-benzylidene-2-deoxy-β-D-glucopyranosyl)-(l→3)-2, 4, 6-tri-O-benzyl-β-D-galactopyranoside (8) via removal of the phthaloyl and O-acetyl groups, followed by N-acetylation and 4, 6-O-benzylidenation. Glycosylation of 8 with methyl 2, 3, 4-tri-O-benzyl-1-thio-β-L-fucopyranoside (9) gave the α-glycoside (10), which was transformed by reductive ring-opening of the benzyliderie acetal into the acceptor (11). Dimethyl(methylthio)sulfonium triflate (DMTST)-promoted coupling of 11 with methyl O-(methyl 5-acetamido-4, 7, 8, 9-tetra-O-acetyl-3, 5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-2, 4, 6-tri-O-benzoyl-l-thio-β-D-galactopyra-noside (12) afforded the desired pentasaccharide (13), which was converted into the α-trichloroacetimidate 16 via reductive removal of the benzyl groups, then O-acetylation, removal of the 2-(trimethyIsilyl)ethyl group and treatment with trichloroacetonitrile. Condensation of 16 with (2S, 3R, 4E)-2-azido-3-O-benzoyl-4-octadecene-l, 3-diol (18) gave the β-glycoside 19, which was transformed into the title compound 21, via reduction of the azido group, coupling with octadecanoic acid, O-deacylation and hydrolysis of the methyl ester group. On the other hand, O-deacylation of 13 and subsequent hydrolysis of the methyl ester group gave the pentasaccharide epitope 17. 相似文献
10.
A synthesis of N-acetylneuraminic acid ( 1 ) and of N-acetyl-4-epineuraminic acid ( 2 , R = H) from 2-acetamido-4,6-O-benzylidene-1,2-dideoxy-1-nitro-D -mannopyranose ( 3 ) and 2-acetamido-1,2-dideoxy-4,6-O-isopropylidene-1-nitro-D -mannopyranose ( 4 ), respectively, is described. Michael addition of 3 and 4 to tert-butyl 2-(bromomethyl)prop-2-enoate ( 5 ) and subsequent hydrolytic removal of the NO2 group gave the 4-nonulosonate tautomers 6 / 7 and 8 / 9 , respectively (Scheme). Stereoselective reduction of 6 / 7 and 8 / 9 with NaBH4/AcOH in dioxane/H2O yielded 12/13 (94:6) and 14/15 (92:8), respectively. Reduction of 6 / 7 and 8 / 9 in the absence of AcOH or in EtOH gave 12 / 13 (15:85) and 14 / 15 (15:85), respectively. Ozonolysis of 12 and 13 followed by hydrolysis gave tert-butyl neuraminate 22 and tert-butyl 4-epineuraminate 24 , respectively. Ozonolysis of 14 / 15 , separation of the products 20 and 21 , and hydrolytic removal of the isopropylidene groups gave 22 and 24 , respectively. The tert-butyl ester 22 was saponified to give 1 , which was further characterized as the methyl ester 23 . Saponification of 24 gave the crude 4-epimer of 1 , which was converted into the stable Na salt 2 and also into the methyl ester 25 . 相似文献
11.
Quinazolinecarboxylic Acids. Synthesis of Alkyl [2-(Ethoxycarbonyl)-3,4-dihydro-4-oxoquinazolin-3-yl]-, [2-(Ethoxycarbonyl)quinazolin-4-yloxy]- and (5,6,7,8-Tetrahydro-2-phenylquinazolin-4-ylthio)alkanoates The [(2-aminobenzoyl)amino]alkanoic acids and their esters 1 showed a different reaction behaviour with diethyl oxalate. Compound 1 (n = 2,3) was converted into the quinazolinylalkanoates 3 . o-Aminohippurate yielded with ethyl (chloroformyl)formate a mixture of the amide 4 and the cyclized quinazolinone 7b . Ethyl 3,4-dihydro-4-oxoquinazoline-2-carboxylate ( 6 ) reacted with 2-bromoalkanoates, in the presence of NaH, to the [2-(ethoxycarbonyl)-3,4-dihydro-4-oxoquinazolin-3-y1]acetates 7 in the case of alkyl bromoacetate, and to the O-alkylated derivatives 8 with the ethyl 2-bromopropionate and -butyrate. 2-Aminobenzamide ( 5 ) gave with ethyl 3-(chloroformyl)-2-propenoate and methyl 3-(chloroformyl)propionate the amides 9 or 11 , respectively, and not the expected quinazolinones. The cyclized product 12 was obtained from 11 and ethyl bromoacetate. Tetrahydroquinazolin-4(3H)-thione 14 was synthesized by the reaction of 13 with NH3, and it was alkylated at the S-atom with bromoalkanoates to 15 . The hydrazide 16 was synthesized from 15b with hydrazine hydrate. 相似文献
12.
Akihiko Kameyama Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(4):549-560
ABSTRACT The first total synthesis of tumor-associated glycolipid antigen, sialyl Lewis X is described. Glycosylation of 2-(trimethylsilyl)ethyl O-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (1) with methyl 2,3,4-tri-O-benzyl-1-thio-β-L-fuco-pyranoside (4) gave the α-glycoside (5), which was converted by reductive ring-opening of the benzylidene acetal into the glycosyl acceptor (6). Dimethyl(methylthio)sulfonium triflate-promoted coupling of 6 with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-D-galactopyranoside (7) afforded the desired hexasaccharide 8 in good yield. Compound 8 was converted into the α-trichloroacetimidate 11, via reductive removal of the benzyl groups, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile, which, on coupling with (2S, 3R, 4E)-2-azido-3-O-benzoyl-4-octa-decene-1,3-diol (12), gave the β-glycoside 13. Finally, 13 was transformed, via selective reduction of the azide group, condensation with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into the title compound 16. 相似文献
13.
Syntheses and Ring-Enlargement Reactions of 2-(4-Hydroxyalkyl)-2-nitrocycloalkanones Syntheses of the title compounds were achieved by [Pd{P(C6H5)3}4]-catalyzed reaction of 2-nitrocycloalkanones 3 with vinyloxirane followed by catalytic hydrogenation. By another route, the known methyl 4-(1-nitro-2-oxocycloalkyl)butanoates 6 were reduced to the corresponding aldehydes 7 which by NaBH4 reduction or methylation with (CH3)2Ti(i-Pr)2 were transformed to the alcohols 5 and 8 , respectively (Saheme 1). Treatment of 5 and/or 8 with KH/THF under reflux gave, via a 7-membered intermediate, the nitrolactones 12 and oxolactones 13 (Scheme 3). Compared with similar reactions running via 5- or 6-membered intermediates (see 1 and 2 ), the yields are distinctly lower. The natural occurring 12-tridecanolid ( 14 ) was synthesized. 相似文献
14.
A convenient synthesis of furo[3,2-b]pyridine and its 2- and 3-methyl derivatives from ethyl 3-hydroxypiconate ( 1 ) is described. The hydroxy ester 1 was O-alkylated with ethyl bromoacetate or ethyl 2-bromopropionate to give the diester 2a or 2b . Cyclization of compound 2a afforded ethyl 3-hydroxyfuro[3,2-b]pyridine-2-carboxylate ( 3 ) which in turn was hydrolyzed and decarboxylated to give furo[3,2-b]pyridin-3-(2H)-one ( 4a ). Cyclization of 2b gave the 2-methyl derivative 4b . Reduction of 4a and 4b with sodium borohydride yielded the corresponding hydroxy derivative 5a and 5b respectively, which were dehydrated with phosphoric acid to give furo[3,2-b]pyridine ( 6a ) and its 2-methyl derivative ( 6b ). 2-Acetylpyridin-3-ol ( 8 ) was converted to the ethoxycarbonylmethyl ether ( 9 ) by O-alkylation with ethyl bromoacetate, which was cyclized to give 3-methylfuro[3,2-b]pyridine-2-carboxylic acid ( 10 ). Decarboxylation of 10 afforded 3-methylfuro[3,2-b]pyridine ( 11 ). 相似文献
15.
2-Amino-3-(o-bromobenzyloxy)pyridine ( 1 ) and ethyl acetoacetate gave 9-(o-bromobenzyl-oxy)-2-methyl-4H-pyrido[1,2-α]pyrimidin-4-one ( 2 ) in 2% yield. When 1 and methyl β-amino-crotonate ( 3 ) were reacted, benzyl ether cleavage occurred and the products were 9-hydroxy-2-methyl-4H-pyrido[1,2-α]pyrimidin-4-one ( 4 ) and its ammonium salt ( 5 ). These observations led to an alternative synthesis in which 2-amino-3-pyridinol ( 6 ) and either 3 or methyl acetoacetate, ( 8 ) in diethylbenzene at 185° gave 4 in 86 and 87% yields, respectively, and the anion of 4 and o-bromobenzyl bromide gave 2 in 61% yield. Even in diethylbenzene at 185°, 1 and 8 gave only trace amounts of 2 . Thus, o-bromobenzylation of the 3-hydroxyl group in 6 markedly decreased the reactivity of the amino group in 6 toward reactions with acetoacetic esters. 相似文献
16.
Xue-Feng Pei Nigel H. Greig Judith L. Flippen-Anderson Sheng Bi Arnold Brossi 《Helvetica chimica acta》1994,77(5):1412-1422
Oxindole 11 , obtained on 3-[2′-(dimethylamino)ethyl]alkylation of oxindole 12 , yielded, on stereoselective reduction with sodium dihydridobis(2-methoxyethoxy)aluminate, aminoalcohol 8 (Scheme 2). The quaternary methiodide 10 , obtained from 8 with MeI, gave, in nucleophilic displacements concurring with a Hofmann elimination, (±)-esermethole 6 , (±)-5-O-methylphysovenol ( 14 ), (±)-5-O-methyl-1-thiaphysovenol ( 15 ), and (±)-1-benzyl-1-demethylesermethole ( 16 ). Syntheses of (±)-1-benzyl-1-demethylphenserine ( 18 ), (±)-1-demethylphenserine ( 19 ), and (±)-phenserine ( 4 ) from 6 and 16 are described. Optically active 8a and 8b , obtained by chemical resolution, similarly gave the enantiomers 6a and 14a–16a of the (3aS)-series (prepared earlier from physostigmine ( 1a )) and their (3R)-enantiomers. The anticholinesterase activity of (±)- 4 , (±)- 18 , and (±)- 19 was compared with that of their optically active enantiomers. 相似文献
17.
New Approaches to Some Aromatic Retinoids Starting from 2,3,5-trimethylphenol ( 2 ), two pathways to ethyl (all-E)-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethylnona-2,4,6,8-tetraenoate ( 1 ) and to some of its (Z)-isomers have been developed. The first one is based on a Pd(O)-catalyzed arylation of (Z)-3-methylpent-2-en-4-yn-l-ol ( 6 ) with 4-bromo-2,3,5-trimethylanisol ( 5 ). The acetylenic C15?alcohol 9 was transformed into the corresponding acetylenic phosphonium salt 10 , which was catalytically hydrogenated to the olefinic Wittig salt. Wittig olefination led, then, to the (6Z, 8Z)- and (4Z, 6Z, 8Z)-isomers, 7 and 8 , respectively. In a second approach, Friedel-Crafts reaction of 3-methylpent-l-en-4-yn-3-ol with the 2,3,5-trimethylanisol gave a C15-intermediate with a terminal C?C bond in the side chain. After deprotonation and reaction with a C5 aldehyd, the corresponding C20-intermediate could be isolated in high yield. Finally, further conversion led predominantly to the (all-E)-retinoid, accompanied by its (9Z)- and (13Z)-isomers. 相似文献
18.
4-Hydroxy-7-methoxy-3-[(m-methoxyphenylimino)-phenylmethyl]-2-quinolone ( 6 ) was a by-product of the condensation of ethyl benzoylacetate and m-anisidine; no corresponding products were obtained from p- and o-anisidine. From o-anisidine, 2-phenyl-8-methoxy-4-quinolone ( 1c ) was isolated and characterized; the same reaction also gave 2-phenyl-4-o-anisidyl-1-8-methoxy-quinoline ( 11 ) and the Schiff base ( 14 ) as by-products; the crotonamide (15) also isolated, is a possible intermediate of the cyclization. The direct condensation of anisidines with ethyl benzoylacetate in diphenyl ether and the transformations of some intermediates were studied. 相似文献
19.
Charles W. Jefford James McNulty Zhi-Hui Lu Jian Bo Wang 《Helvetica chimica acta》1996,79(4):1203-1216
L -Aspartic acid by tosylation, anhydride formation, and reduction with NaBH4 was converted into (3S)-3-(tosylamino)butan-4-olide ( 8 ; Scheme 1). Tretment of 8 with ethanolic trimethylsilyl iodide gave the N-protected deoxy-iodo-β-homoserine ethyl ester 9 . The latter, on successive nucleophilic displacement with lithium dialkyl-cuprates ( → 10a–e ), alkaline hydrolysis ( → 11a–e ), and reductive removal of the tosyl group, produced the corresponding 4-substituted (3R)-3-aminobutanoic acids 12a–e (ee > 99%). Electrophilic hydroxylation of 8 ( → 19 ; Scheme 3), subsequent iodo-esterification ( → 21 ; Scheme 4), and nucleophilic alkylation and phenylation afforded, after saponification and deprotection, a series of 4-substituted (2S, 3R)-3-amino-2-hydroxybutanoic acids 24 including the N-terminal acids 24e ( = 3 ) and 24f ( = 4 ) of bestatin and microginin (de > 95%), respectively. 相似文献
20.
Acidic condensation of 2,4-dimethylfuran with acetaldehyde provided 2,2′-ethylidenebis[3,5-dimethylfuran] ( 7 ) which added 1 equiv. of methyl bromopropynoate to give a major adduct 8 . Regio- and stereoselective hydroboration of the latter 7-oxanorbornadiene derivative followed by alcohol protection and methanolysis of its β-bromoacrylate moiety gave (1RS,2RS,4RS,5SR,6SR,1′RS)-methyl 4-[1′-(3″,5″-dimethylfuran-2″-yl)ethyl]-3,3-dimethoxy-6-exo-[(2-methoxy)ethoxy]-1,5-endo-dimethyl-7-oxabicyclo[2.2.1]heptane-2-endo-carboxylate ( 24 ) (Schemes 2 and 3). Reduction of 24 with LiAlH4, followed by H2O and MeOH elimination gave the 3-methyl-idene-7-oxanorbornan-2-one derivative 26 which underwent 7-oxa ring opening through a SN2′ type of reaction with Me2CuLi (Scheme 4). Stereoselective hydrogenation and ketone reduction provided (1RS, 2SR,3RS,4RS,5RS,6RS,1′SR)-1- [1″-(3 ″,5″-dimethylfuran-2″-yl)]-c-3-ethyl-c-5-[(2-methoxyethoxy)m e-c-ethyl-c-c-5-(2-methoxyethoxy)methoxy]-t-4,t-6-dimethyl-cyclohexane-r-1,c-2-diol ( 32 ), the oxidative cleavage of which with Pb(OAc)4 generated a 6-oxo-aldehyde 33 (Schemes 4 and 5). Chemoselective protection of 33 and chemo- and stereoselective reductions generated (2RS,3RS,4SR,5SR,6SR,7RS)-7-(3′,5″-dimethylfuran-2′-yl)-2-ethyl-6-hydroxy-4-[(2-methoxyethoxy)methoxy]-3,5-dimethyloct-1-yl pivaloate ( 36 ) and its 4-hydroxy 6-epimer 40 (12 and 13 steps, resp., from adduct 8 ; Scheme 5). Oxidation of the furan ring of 36 led to a (2RS,3SR,4RS,5SR,6RS,7RS)-7-ethyl-3,5,8-trihydroxy-2,4,6-trimethyl-octanoic acid derivative 44 , a polypropionate fragment with six contiguous stereogenic centres (Scheme 6). 相似文献