共查询到20条相似文献,搜索用时 375 毫秒
1.
Jack E. Baldwin Robert M. Adlington Bernard J. Rawlings Richard H. Jones 《Tetrahedron letters》1985,26(4):485-488
Practical procedures for the resolution of racemic modification of (1, 2)-and (1, 2)-1-amino-2-ethylcyclopropane-1-carboxylic acid ,,(1, 2)- and (1, 2)-1-amino-2-methylcyclopropane-1-carboxylic acid ,, and (1, 2)- and (1, 2)-1-amino-2-methylcyclopropane-1-carboxylic acid , are described; the structures as ,, and were confirmed by X-ray-crystallographic methods. 相似文献
2.
Reaction of the cyclic 1, 3-dicarboxylic acid derivatives (), () and () with (R)- or (S)-citronellal (/) gives the enantiomeric tricyclic dihydropyrans (), (), () and (), probably via a 100% stereocontrolled intramolecular cycloaddition. 相似文献
3.
Felix H. Cano Concha Foces-Foces Manuel Bernabe Jesus Jimenez-Barbero Manuel Martin-Lomas Soledad Penades-Ullate 《Tetrahedron》1985,41(18):3875-3886
X-Ray and 1H N.M.R. studies on pyranoid rings 1,2--fused to dioxolane rings in acetylated -gluco- and --galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the -gluco but not in the -galactopyranose series. The crystal structure of 3,4,6-tri--acetyl-1,2--(R)--(l-cyano-ethylidene)-α--glucopyranose () and 3,4,6-tri--acetyl-1,2--()-(1-cyano-ethylidene)-α--galactopyranose ()have been determined by X-ray analysis. Lattice parameters for are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened 4C1 and that of the dioxolane ring as distorted E1. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The 1H N.M.R. spectra of and and 3,4,6-tri--acetyl-1,2-O-(S)- and (R)-ethylidene-α--glucopyranose ( and ), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ()-ethylidene-α--galactopyranose ( and ), and 3,4,6-tri--acetyl-1,2--()-and ()-benzylidene-α--glucopyranose ( and ) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the -gluco series , and may be described as flattened 4C1 and that of and as 25. The major solution conformation of the pyranoid ring in all compounds in the -galacto series (,,,) may be described as flattened 41. 相似文献
4.
Reactions of allylides () with nitrile oxides () afforded furanylglyoxylate oxime () and 6H-l,2-oxazine (). Ring transformations of and gave and pyrrolinone (), respectively. 相似文献
5.
Reaction of ,,,-[9]annulene anion () with electrophiles (-) leads to substituted ,,,-1,3,5,7-cyclononatetraenes (-) which are precursors for the preparation of 10- and 10,10′-donor-substituted nonafulvenes (e.g. ). The influence of solvent and temperature on the 1H-nmr spectra of the nonafulvenes - has been investigated. 相似文献
6.
Flow vacuum thermolysis (FVT) of thiophene-2,3-dicarboxylic anhydride () in the presence of 2,3-dimethylbutadiene () gives, in addition to 5,6-dimethylthianaphthene (). small quantities of a dihydrodimethylthianaphthene () and another dimethylthianaphthene () which is probably also formed by dehydrogenation of with chloranil. The partial structures of these minor products are consistent with their being formed by a [2+2]-cycloaddition between and an intermediate aryne, 2,3-didehydrothiophene (), followed by a rearrangement of the resulting adduct and dehydrogenation. FVT of in the presence of 2,5- () or 3,4-dimethylthiophene () also gave a mixture of the dimethylthianaphthenes (, ) which can be rationalized as arising by a [4+2]- and two [2+2]-cycloadditions of the aryne to the thiophenes with subsequent desulfurization. The lack of equilibration of the products , and , was demonstrated and their origin as a function of the structure and reactivity of the aryne discussed. 相似文献
7.
In contrast with the reaction of α-aminonitriles a, the corresponding -acylated α-aminonitriles b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles - or 4(5)-imidazolones , the latter being converted in some cases into imidazo [2,1-]isoquinoline-2,5,6(3)-triones. Reactions of compounds b-f and ethyl chlorooxoacetate provide evidence for a 5(4)-iminooxazole intermediate , which aromatizes to yield 5-aminooxazoles -; however, unaromatizable īntermediates of type - isolable as 5(4)y-oxazolones after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives . 相似文献
8.
The biomimetic reactions of epoxygermacrene-D () with basic alumina afforded three new interesting compounds (, , and ), two of which ( and ) have the same carbon skeleton as that of periplanone-A (), a sexual stimulant for the American cockroach. The remaining one () is a bicyclo[3.1.0]hexane derivative, from whch an axisonitrile-3 type compound () has been produced. Finally, preisocalamendiol () was also converted into . 相似文献
9.
Reaction of the hydroaromatic compounds () and () with lithium-diisopropylamide followed by phenylselenenyl chloride gives the selenides () and () resp. (), which form exclusively the phenols () resp. () after oxidation with 3-chloroperbenzoic acid in the presence of 3,5-dimethoxyaniline (). 相似文献
10.
A new synthesis of the pyranoquinolone alkaloids flindersine (), 8-methoxyflindersine (), N-methylflindersine (), zanthobunglanine () oricine () and veprisine () and the prenylquinolone alkaloids atanine (), preskimmianine () N-methylatanine (), O-methylglycosolone () and N-methylpreskimmianine () is described. 相似文献
11.
Trifluoroethyl cyclohexyl ketone () is prepared by acylation of difluoroethylene () with cyclohexanecarboxylic acid chloride (), followed by Cl→F exchange with potassium fluoride in the presence of triethylbenzyl- ammonium chloride. Bayer-Villiger oxidation of ketone () with trifluoroperacetic acid gives cyclohexyl trifluoropropionate (). 3,3,3-trifluoropropionic acid () is obtained by treatment of () with trimethylsilyl iodide. Condensation of 2,2,2-trifluorodiazoethane () with ethyl glyoxylate () gives mainly ethyl 4,4,4-trifluoro-2-ketobutyric acid ester () which leads after hydrolysis to the corresponding acid (). 相似文献
12.
The reaction of indoles () with superoxide ion resulted in ring cleavage to give -formyl and -acylaminoketones () or N-acylanthranilic acid () and ring expansion yielding 2-quinolones (). All reactions are chemiluminescent except that of 2-methylindole (), which gave a coupled product (). 相似文献
13.
Iodine-mediated cyclization of (Z)- and (E)-{=D}-ribohept-2-enonates and gave exclusively the β-ribofuranose and α-ribofuranose derivatives and , respectively. Cyclization of the (Z)- and (E)-2-heptene-1-ol derivatives and gave ribofuranose products ( and ) and a ribopyranose (), respectively. 相似文献
14.
Lithiation of both ()- and ()-3-trimethylsilyl-2-propenyl ,-diisopropyl carbamate 2 affords the (2) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1)-(3*4*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3)- or with (3)-configuration. So just by reagent selection for each of the two steps, (1,3)-, (1,3)-, (1,3)-, or (1,3)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7% 相似文献
15.
《Tetrahedron》1986,42(8):2345-2350
In the reactions of 2-thioxo-- and -3,1-perhydrobenzoxazines (, ) with methyl iodide the hydrogen iodide formed in the S-methylation process brings about ring-opening and gives iodomethylthiolcarbamates (, ). Under similar conditions, the thioether salts (, ) of the structurally isomeric - and -2-thioxo-1,3-perhydrobenzoxazines, corresponding to the unstable intermediates in the former reactions, are stable. Under more vigorous conditions, the isomer thioether salt is transformed into the corresponding -and -l,3-perhydrobenzoxazin-2-ones (, ) by ring-opening and subsequent ring-closure, whereas the isomer gives only -1,3-perhydrobenzoxazin-2-one (). 相似文献
16.
Reaction of () and () with the acetal () in presence of trimethylsilyl trifluoromethanesulfonate at ?70° C gives the α-glucosides () and (), whereas () and () lead to the β-glucosides () and (). At 0° C reaction of () with the acetals () gives exclusively the α-glucosides (). 相似文献
17.
Miyoji Hanaoka Shingo Yasuda Kazuyoshi Nagami Keiko Okajima Takeshi Imanishi 《Tetrahedron letters》1979,20(39):3749-3752
Irradiation of the berberinephenolbetaines (, , and ) effected valence tautomerization to give the 8,14-cycloberbines (, , and ), the aziridine derivatives, in high yield. The 8,14-cycloberbines were efficiently converted to the spirobenzylisoquinolines by regioselective C bond cleavage. 相似文献
18.
Ignacio H. Sánchez María Isabel Larraza Fernande Basurto Ricardo Yaf?ez Salvador Avila Ricardo Tovar Pedro Joseph-Nathan 《Tetrahedron》1985,41(12):2355-2359
(±)--methylperezone () was obtained by selective oxidative demethylation of (±)-leucoperezone trimethyl ether (). Compound () was prepared by condensation of 2,3,5-trimethoxytoluene () with 6-methyl-5-hepten-2-one, followed by reductive removal of the tertiary alcohol. The aromatic precursor was prepared in four steps from 2,3-dimethoxytoluene () and, alternatively, in three steps from 5-bromoveratraldehyde (). Racemic and were directly compared with the optically active molecules prepared from natural R(-)-perezone (). 相似文献
19.
6, 7-Dimethoxy-2-l,3-benzothiazine derivatives (, ) react with substituted acetyl chlorides to give angularly condensed β -lactams (-, , ). The compound was epimerised to the derivative . From the interaction of 2-phenyl-6,7-dimethoxy-4-1,3-benzothiazine () and α -chloro-phenylacetyl chloride two stereoisomeric β -lactam derivatives (, ) were isolated, whereas in the other cases studied the reactions leading to β -lactams proved to be stereospecific. Analogous reactions of -methyl-6,7-dimethoxy-2-l,3-benzothiazine () furnished the enamides ,, . Structures of the new compounds and configurations of the diastereomers were elucidated by IR and NMR spectroscopy. 相似文献
20.
Giovanni Fronza Claudio Fuganti Piero Grasselli Giuseppe Pedrocchi-Fantoni 《Tetrahedron letters》1981,22(50):5073-5076
The synthesis of the N-benzoyl derivatives of - (10),- (13) and - (-vancosamine) (12) 2,3,6-trideoxy-3--methyl-3-aminohexose from the (2,3) diol (1) prepared in fermenting bakers' yeast from α-methylcinnamaldehyde and acetaldehyde is reported 相似文献