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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.
The synthesis of 3-acetylcyclohexanones , , has been realized by conjugate addition of lithiated cyanohydrin ether to 2-cyclohexenones , , in THF-HMPA, even if 3-substituted. 3-benzoylcyclohexanones , , are obtained from and , , in THF with excellent yields. 相似文献
3.
Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′, 2, 2″, 5, 6)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′, 2, 5, 6)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran. 相似文献
4.
Stereospecific conversion of β-hydroxyallylglycine derivatives into (2, 3, 4) 1 and (2, 3, 4) 2 halo- or mercuri-lactonization has been described. 相似文献
5.
The Sharpless asymmetric epoxidation was used for the synthesis of D--dihydrosphingosine triacetate and (2, 3, 5)-2-acetamino-5,9-dimethyl-8-decene-1,3-diol, whose 13C-NMR study coupled with biogenetic consideration enabled us to propose (2, 3, 5,13, 14)-stereochemistry for aplidiasphingosine. 相似文献
6.
For 12-- locked retinal analogues, thermal equilibria are established between 11-, 13--1c and 13--2c and between 9-, 11-, 13--1d and 9-, 13--2d; a photoisomerization occurs to transform 2c to --2a and 2d to 9--2b 相似文献
7.
Lindlar hydrogenation of substituted methyl (,)-deca-7,9-dien-2-ynoates and substituted methyl (,)-undeca-8,10-dien-2-ynoates affords selectively the corresponding (,,)-trienes. 相似文献
8.
The title compounds , , and have been synthesised by oxygen-alkylation of the alkoxy-substituted N-methylene amides , , , and using triethyloxonium salt . The stereochemistry of the new salts is discussed in terms of an competition between the 2-aza-allenium- and the 2-aza-allyl-cation structures (I) and (II). 相似文献
9.
The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid (, ; ; , ) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-,,, (R)(–)-). 相似文献
10.
tert-Butyl azidoformate () reacts with the conjugate bases of , , (R1 = R2 = CH3), and (R1 = CH3, R2 = H) to give products [, , , and , respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives. 相似文献
11.
The Claisen rearrangement permits the stereoselective formation of butyrolactone or through the utilization of enantiomeric lactone and enantiomeric alcohols , ent-, , and ent-. 相似文献
12.
Reactivity of pyridazines , , , towards ethoxycarbonylradical (generated by redox decomposition of oxyhydroperoxide of ethylpyruvate) was studied. Application of this type of homolytic substitution for synthesis of hitherto not accessible pyridazine carboxylic acid esters , , , , , , , is demonstrated. In addition improved synthesis of diethyl 4,5-pyridazinedicarboxylate () is proposed. 相似文献
13.
Direct chlorination of 2-(2H-hexafluoropropyl)-tetra- hydrofuran gave high yield of 2-(2-chlorohexafluoropropyl)- pentachloro-2,5-dihydrofuran . Bromination of gave very complex mixture of products, from which three compounds, . 2-bromo-5-(2H-hexafluoropropyl)-furan , 3-bromo-5-(2H-hexafluoropropyl)-furan , and 2,4-dibromo-5-(2H-hexafluoropropyl)furan were isolated. Exchange fluorination of with dry KF at 240 – 300° led to a stepwise substitution of fluorines for chlorines to give mixtures of chloro-fluoro-2-(2-chlorohexafluoropropyl)-dihydrofurans ,, and , together with small amounts of 2-(2-chlorohexafluoropropyl)-3,4,5-trichlorofuran .Exchange fluorination of 3,4-dihalo-2,2,5,5-tetrafluoro- 2,5-dihydrofurans and led to a substitution of fluorine for one vinylic halogen to give 3-halo-2,2,4,5,5-pentafluoro-2,5-dihydrofurans and in good yields.Compounds – were characterised by n.m.r., m.s., and i.r. spectroscopy and elemental analysis. 相似文献
14.
A synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate () and propionate () is described. (2S)-2-Methyldecan-1-yl lithium () was reacted with (3S,4S)-3,4-dimethyl-γ-butyrolactone () to yield the ketoalcohol which upon Huang-Minlon reduction furnished (2S,3S,7S)-3,7-dimethylpentadecan-2-ol (). Acylations gave the esters and . The (2S)-2-methyldecan-1-yl lithium was obtained via asymmetric synthesis. The chiral lactone was obtained from (2S,3S)-trans-2,3-epoxybutane and dimethyl malonate. 相似文献
15.
Novel carbon nucleophilic displacement reactions on Kamiya's azetidinone disulfide and the synthesis of the C-2 modified penams , and from the intermediates , , and are described. 相似文献
16.
Reaction of bicyclophosphane with glycol , glycerol , erythritol , L(-)arabitol and dulcitol leads to the corresponding per-alkoxybicyclophosphoranes - which are in tautomeric equilibrium with the phosphates forms ′ - ′.The amount of these latters increases regularly from traces to 24%. 相似文献
17.
Three fungal metabolites with a common structural feature as prenylated phenols were synthesized in their naturally occurring and optically active forms: ascochlorin [(2',4',1',2',6')-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[5'-(1',2',6'-trimethyl-3'-oxo-cyclohexyl)-3'-methyl-2', 4'-pentadienyl] benzaldehyde], ascofuranone [(2',6',1')-(-)-5-chloro-2, 4-dihydroxy-6-methyl-3-[7'-(3',3'-dimethyl-4'-oxo-2'-oxacyclopentyl)-3',7'-dimethyl -2', 6'-heptadienyl] benzaldehyde] and ascofuranol [(2',6',1',4')-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[7'-(3', 3'-dimethyl-4'-hydroxy-2'-oxacyclopentyl)-3', 7'-dimethyl-2',6'-hepta-dienyl]benzaldehyde ]. (+)-Ascofuranone and (+)-ascofuranol were also synthesized. By the present synthesis the absolute configuration of the natural (-)-ascofuranol was established as (1',4'). 相似文献
18.
Reaction of dimetalated succinamides with benzyl halides and aromatic aldehydes provides short routes to diverse lignan natural products , , and , including the human urinary metabolites () and (). 相似文献
19.
Toshiaki Nishida Inger Wahlberg Kerstin Nordfors Carmen Vogt Curt R. Enzell 《Tetrahedron letters》1984,25(12):1299-1302
Proton-proton shift correlated 2D-NMR spectroscopy has been used to determine the structure of a new tobacco cembranoid as (1,2,4,6,7)-4,6-dihy-droxy-2,7,12(20)-cembratrien-11-one (1). This assignment has been verified by chemical means. 相似文献
20.
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