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1.
(±)-O-methylperezone (1b) was obtained by selective oxidative demethylation of (±)-leucoperezone trimethyl ether (4a). Compound (4a) was prepared by condensation of 2,3,5-trimethoxytoluene (5e) with 6-methyl-5-hepten-2-one, followed by reductive removal of the tertiary alcohol. The aromatic precursor 5e was prepared in four steps from 2,3-dimethoxytoluene (5a) and, alternatively, in three steps from 5-bromoveratraldehyde (6a). Racemic 1b and 4a were directly compared with the optically active molecules prepared from natural R(-)-perezone (1a).  相似文献   

2.
A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.04,7] nonane, 1) was achieved. The stereochemistry of (+)-lineatin was established as 1R, 4S, 5R, 7R by an X-ray crystallographic analysis of an intermediate 15.  相似文献   

3.
The structure of reductiline, a metabolite of a variant of Streptomyces orientalis was elucidated as (1) based on chemical and spectroscopic evidence. Transformation of an antitumor antibiotic reductiomycin (2) into reductiline (1) was carried out. Synthesis of reductiline (1) was achieved starting from β-cyanopropionaldehyde dimethylacetal.  相似文献   

4.
The synthesis of the 2,4,6-cycloheptatrienyl ketones 1a1e by two alternative routes is reported: Route 1): The adducts 3a–c from the phenyl(trimethylsiloxy)-acetonitriles 2a–c, known as “umpolung” reagents, and tropylium tetrafluoroborate are cleaved by triethylammonium fluoride to form the aromatic cycloheptatrienyl ketones 1a1c. Route 2): the phenyl, methyl, and cyclopropyl ketone (1a, 1d, 1e) are prepared by treatment of the acid chloride 7 with the corresponding organomanganese iodides RMnI (8a, 8d, 8e). The Fe-catalyzed coupling reaction of the acid chloride 7 with a Grignard reagent was also used for the preparation of ketone 1b.  相似文献   

5.
Total synthesis of (±)-sesbanine (1) was carried out using γ-addition of ketene silyl acetal of methyl 3-cyclopentenecarboxylate to quaternized methyl nicotinate. The resulting 1,4-dihydropyridine (7) was oxidized with DDQ to give 4-substituted nicotinate (2) and 2 was converted to alcohol (8) by stereoselective oxymercuration followed by treatment with ammonia to give 1.  相似文献   

6.
The photochemical behavior of cis-1,2-dihydrophthalide (1) and its 1,2-trimethylene derivative (4) was studied. Besides bicyclo[2.2.0]hexene formation in both cases, (1) transforms into its trans isomer (3) whereas (4) undergoes a 1,2-shift to (7).  相似文献   

7.
Biogenetic-type synthesis of (±)-dictyopterene A (1) was achieved employing 1,cis-5-undecadien-3-ol (2) postulated to be a biosynthetic intermediate of 1: this synthesis means that transformation of dictyoprolene (4) into dictyopterene A (1) was formally made.  相似文献   

8.
9.
An azaanalog of adamantene, 2-azaadamant-1-ene (1) and 4-azaprotoadamant-3-ene (7) were generated in the nonstatistical ratio via photolysis of 3-azidonoradamantane (2). The highly strained 1 and 7 could not be isolable but were trapped by MeOH. Acidolysis of 2 was also reported, and discussed in comparison with the photolysis.  相似文献   

10.
《Tetrahedron》1986,42(16):4413-4420
(2S,3R,1'R)-Stegobinone [2,3-dihydro-2,3,5-trimethyl-6-(1'-methyl-2'-oxobutyl)-4H-pyran-4-one], the pheromone of Stegobium paniceum L., was synthesized with stereocontrol at C-2 and C-1' starting from ethyl (R)-3-hydroxybutanoate and methyl (R)-3-hydroxy-2-methylpropanoate. The dihydro-γ-pyrone ring of the pheromone was constructed by an intramolecular acylation followed by acid-catalyzed cyclization.  相似文献   

11.
The optical activity of (1S,5R-1-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one (1) is determined by partial photoresolution of the racemate with circularly polarized laser light; although a rearranged, optically active product was also formed, isolation of the 1 enantiomers was note required.  相似文献   

12.
Practical procedures for the resolution of racemic modification of (1R, 2S)-and (1S, 2R)-1-amino-2-ethylcyclopropane-1-carboxylic acid 1a,b,(1R, 2S)- and (1S, 2R)-1-amino-2-methylcyclopropane-1-carboxylic acid 2a,b, and (1R, 2R)- and (1S, 2S)-1-amino-2-methylcyclopropane-1-carboxylic acid 3a,b are described; the structures as 1a,2a, and 3a were confirmed by X-ray-crystallographic methods.  相似文献   

13.
Upon photooxidation bicyclopropylidene (1) yields spiro[2.3]hexan-4-one (4) and 7-oxatrispiro[2.0.2.1]heptane (6). The formation of these is rationalized. Authentic 6 was prepared by epoxidation of 1, and 4 by isomerization of 6.  相似文献   

14.
1-Methyl-2-(1′-cyano-1′-trimethylsilyloxy)alkyl-1H-imidazoles (2) were easily prepared from the corresponding stable carbonyl compounds, 1-methyl-2-acyl- 1H-imidazoles (1). When the quarternary salts of 2 were treated with various nucleophiles, reactive acyl species, which was presumed to be acylcyanide (12), was generated in situ under CC bond fission to result in producing the corresponding acylated compounds (510) in good yields.  相似文献   

15.
The acid catalysed cyclization of β-hydroxy selenide (4), which was prepared from nerolidol (1) via the epoxide (3), was carried out to give bicyclic ether (5) directly which was further transformed into caparrapl oxide (6).  相似文献   

16.
A preparative route to cis- and trans-1,2-dibromocyclopropane (1) was developed via the Hunsdiecker reaction of silver cyclopropane-1,2-dicarboxylate (2). Cis- and trans-2 gave the same ratio of cis- and trans-1 (1:3.2). The mechanism of this reaction is briefly discussed.  相似文献   

17.
The structures of three new prenylphenyl propanoids, wutaiensol (1), wutaiensal (2), and methyl demethoxywutaiensate (4) were established by correlating with S-rutaretin methyl ether (9) or S-marmesin (24) by chemical means. The structure of wutaialdehyde (3), a related compound, was also established by total synthesis of the racemate and by correlating with 1. Preliminary piscicidal test on these compounds disclosed that 2 and 4 are weakly bu distinctly positive.  相似文献   

18.
In contrast to simple imidazoles, 1-methy1–2,4,5-triphenylimidazole (1) produced stable oxetane photoadducts 3b - e with good efficiency upon irradiation in the presence of benzophenone derivatives 2b - e in acetonitrile solution. Irradiation in the solid-phase was also studied. The oxetanes 3b - e readily underwent cycloreversion by acid catalysis or by heating.  相似文献   

19.
Methyl 4-0-benzoyl-6-bromo-6-deoxy-α-D-glucopyranoside (1, Figure 1) was converted, via the corresponding ditosylate 2, into methyl 2,3-di-0-p-toluenesulfonyl-4-0-benzoyl-6-S-acetyl-6-thio-α-D-glucopyranoside (3) by a selective nucleophilic displacement of 6-bromo-group with thioacetate. Unexpectedly, on treating the compound 3 with an excess of sodium methoxide in benzene-methanol (1:1) at room temperature, methyl 2-0-p-toluenesulfonyl-4,6-thioanhydro-α-D-gulopyranoside (4) was obtained in a yield of 84%. In order to determine the structure of the relatively unstable oily product 4, some stable crystalline derivatives (5, 6 and 7) were prepared. Detailed analysis of the 1H-NMR-spectra (200 MHz) of 6 and 7 gave the conclusive evidence for the structure of 4 A self-imposing mechanism of the clean and smooth transformation of 3 to 4 is proposed, involving: a) formation of 9 (Figure 2) as a crucial intermediate and b) a highly regioselective epoxide opening in 9 (at C-4) by an intramolecular nucleophilic attack of the mercaptide anion from C-6.  相似文献   

20.
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