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1.
(1,5)-(-)-Karahana ether (8,8-dimethyl-2-methylene-6-oxabi-cyclo[ 3.2.1]octane) and (1,5)-(-)-karahana lactone (8,8-dimethyl-2-methylene-6-oxabicyclo [3.2.1]octan-7-one) were synthesized from ()-3-hydroxy-2,2-dimethylcyclo-hexanone. The natural karahana lactone was shown to be almost racemic (. 1.3 % e.e.). 相似文献
2.
Hideo Kigoshi Makoto Ojika Yoshikazu Shizuri Haruki Niwa Kiyoyuki Yamada 《Tetrahedron letters》1982,23(51):5413-5414
From a red alga (10, 11)-(+)-squalene-10, 11-epoxide was isolated and its asymmetric synthesis has been achieved starting from -farnesol. 相似文献
3.
Pinacol -1-trimethylsilyl-1-propene-3-boronate reacts with aldehydes to form (±)-(*,*)-3-trimethylsilyl-4-hydroxy-1-alkenes, which can be deoxysilylated stereoselectively to either 98% or 99% 1,3-dienes, including the separate components of the red bollworm moth pheromone. 相似文献
4.
J Leitich 《Tetrahedron letters》1980,21(32):3025-3028
The relative rates of formation of and [2+2]cycloadducts of benzyne to , - and , -1,5-cyclooctadiene, - and -cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described. 相似文献
5.
The 1H and 13C nmr spectra of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d6 or alkaline D2O, clearly show that it exists in a --conformation with carboxyl groups, thus being the first case of - preference of a bicyclo[3.3.1] nonan-9-one due to the presence of ,-2,4- substituents. 相似文献
6.
A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.04,7] nonane, ) was achieved. The stereochemistry of (+)-lineatin was established as 1, 4, 5, 7 by an X-ray crystallographic analysis of an intermediate . 相似文献
7.
Lithio reagents derived from 1-triisopropylsilylpropyne () and 1,3--[triisopropylsilyl]propane () are effective for the synthesis of or terminal enyne units (CHCHCCH) and for carboncarbon bond formation with halides, aldehydes, ketones, epoxides, and α,β-enones. 相似文献
8.
N-Acyl derivatives of ,-acosamine and ,-ristosamine were synthesized with high stereo selectivity utilizing intramolecular Michael addition of γ- and δ-carbomoyloxy-α,β-unsaturated esters. 相似文献
9.
A new plant growth-promoting sterol was isolated from immature seeds of . The structure was elucidated as (22, 23-2α, 3α, 22, 23-tetrahydroxy-B-homo-7-oxa-5α-ergost-24(28)-en-6-one . 相似文献
10.
1,3,7,9,11,12,14-Heptazapentacene-2,4,8,10 (14,3,9,12)-tetraones (mixed flavins) were prepared by the cyclization of 1,5-dihydro-8-[N-alkyl-N-(5-nitrouracil-6-yl)-amino-5-deazaflavins with Vilsmeier reagent. The mixed flavins oxidized alcohol under neutral condition in sunlight and a remarkable autorecycling was observed. 相似文献
11.
Marino Cavazza Maurizio Zandomeneghi Crescenzo Festa Enrico Lupi Manuela Sammuri Francesco Pietra 《Tetrahedron letters》1982,23(13):1387-1390
The optical activity of (1,5-1-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one () 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 enantiomers was note required. 相似文献
12.
A novel olefin metathesis sequence permits ready access to functionalised , , -tricyclo [6.3.0.02,6] undecane based bis-enones. These bis-enones have been shown to undergo cage cyclisation in sunlight with remarkable ease and efficiency. 相似文献
13.
A unified approach to either (22)- or (22)-hydroxy-23-acetylenic steroid side chains is described which relies on the concept of the stereochemical transmission via the [2,3]-Wittig sigmatropic rearrangement. 相似文献
14.
Terence C. Smale 《Tetrahedron letters》1984,25(27):2913-2914
Incorporation of a chiral ketone into the established tetrahydro-1,3-oxazine route to thienamycin analogues, has enabled the isolation of single enantiomers having the naturally occurring ()-configuration at the bridgehead. 相似文献
15.
Giovanni Fronza Claudio Fuganti Piero Grasselli Giulio Marinoni 《Tetrahedron letters》1979,20(40):3883-3886
The enantiomeric alcohols () and (), obtained from (2,3) tartaric acid and, respectively, -threonine, have been used to construct the C6, enantiomeric deoxy amino sugar derivatives () and () 相似文献
16.
An asymmetric synthesis of ()-(?)-mevalolactone in over 87% enantiomeric purity is described. 相似文献
17.
Depending upon the experimental conditions, t-butyl (1,5,7,8)-1-ethoxycarbonyl-8-hydroxy-2-oxa-6-azabicyclo[3.2.0]octane-7-carboxylate (2a) reacts with methanesulphonyl chloride to give predominantly the -methanesulphonyl derivative (2b), the -methanesulphonyl derivative (3a), or the -(methanesulphonyl)methane-sulphonyl derivative (6a). 相似文献
18.
A stereospecific, highly efficient, generally applicable synthesis of - and -1-alkoxy-1,3-butadienes involving dehydrative decarboxylations of 4,5-unsaturated-2-alkoxy-3-hydroxy-carboxylic acids is described. 相似文献
19.
The 6-hydroperoxy-1,4-cyclooctadiene (), which is formed in the photosensitized oxygenation of 1,5-cyclooctadiene (), affords on further singlet oxygenation 5,8-dihydroperoxy-1,3-cyclooctadiene (), which via triphenylphosphine reduction leads to -5,8-dihydroxy-1,3-cyclooctadiene () and subsequent pyridinium chlorochromate oxidation to 1,3-cyclooctadien-5,8-dione (). 相似文献
20.
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