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1.
Condensation of 3-fluoro-2-butanone () with alkyl diethylphosphonoacetates () gave alkyl 4-fluoro-3-methyl-2-pentenoates (). Addition of bromine yielded alkyl-2,3-dibromo-4-fluoro-3-methylpentanoates () which were dehydrobrominated to alkyl 2-bromo-4-fluoro-3-methyl-2- pentenoates (). Since these compounds could not be hydrogenated to the desired alkyl 2-bromo-4-fluoro-3-methylpentanoates (), another route was taken. The esters were hydrogenated to alkyl 4-fluoro-3- methylpentanoates () which were converted to their carbanions. Treatment with bromine gave esters , and iodine gave alkyl 4-fluoro-2-iodo- 3-methylpentanoates (). Esters and were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates () whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (). Hydrolysis afforded γ-fluoroisoleucine (). 相似文献
2.
E.G. Frandsen 《Tetrahedron》1977,33(8):869-873
The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2,5-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2-benzo [b]-pyran-2,4-diones. 相似文献
3.
Treatment of , , and with methyllithium affords , ; , ; and respectively in serviceable yields carbenoid cyclization. 相似文献
4.
Base-catalyzed reaction of 5-acylmethyl-2,5-di--butyl-4-oxa-2-cyclopentenones selectively derived from 4-alkyl-2,6-di--butylphenols three steps involving oxygenation, acetylation, and acid-treatment gave 3-alkyl-2,5-di--butyl-2,4-cyclopentadienones in excellent yield. 相似文献
5.
3-Methylisoxazolo[4,5-c]pyridine on reduction with BH3:THF gave, via the isolable complex , the tetrahydroisoxazolopyridine . The presence of two chlorine atoms at the 4 and 6 positions directed borane attact to the isoxazole ring, yielding the aminoethylpyridine . Both types of reduction were obtained with 6-chloroisoxazolo[4,5-c]pyridine . 相似文献
6.
A short and convenient synthesis of phosphatidyl-α-diglucosyldiglyceride (i.e. compound ) and two related Streptococci glycolipids (i.e. compounds and ) will be presented. 4',6'-Tetraisopropyl-disiloxane-1,3-diyl (TIPS) protected α-glucosyl diglyceride (i.e. compound ) turned out to be a suitable protected precursor. Thus, compound was selectively condensed with glucosyl bromide to afford . Removal of the protecting groups from gave glycolipid . The “dynamic” properties of the TIPS pro- tecting group were utilized to convert 4',6'-TIPS protected into 3',4'- TIPS protected derivative . Compound could then be condensed with either a stearoyl fatty acid or a phosphatidyl moiety to give the fully protected derivatives and , respectively. Finally, removal of all the protecting groups from and afforded the glycolipid and glycophospholipid , respectively. 相似文献
7.
Acylation of 4-aryl-2,6-di--butyl- and 2,4,6-tri--butyl- 6-hydroperoxy-2,4-cyclohexadienones gave unexpected products, 4-acyloxy-5,6-epoxy-2-cyclohexenones and 2-acyloxy-5,6-epoxy-3-cyclohexenones. The reaction involves a rapid homolysis of the peroxy bond of peroxy esters transiently formed in the pre-existing slow step. 相似文献
8.
The superoxo complex [Co(CN)5O2]3- was found to act as a reducing agent towards quinones. One-electron reduction took place with -quinones whereas two-electrons reduction with -quinones. 3,5-Di--butyl--benzoquinone gave the corresponding semiquinone Co(III) complex quantitatively. 相似文献
9.
Alcohols and , prepared from , underwent completely stereospecific etherification to give 1-oxacephams and , which were converted into the 1-oxacephem nucleus via and . Functionalization at C-3′ in and was unsuccessful. 相似文献
10.
Herbert L. Holland David B. MacLean Russell G.A. Rodrigo Richard F.H. Manske 《Tetrahedron letters》1975,16(49):4323-4326
The reduction product of dehydrocordrastine, , with di-isobutylaluminum hydride spontaneously rearranged to the spirobenzylisoquinolines and , analogous to the alkaloids sibiricine (), corydaine (), and yenhusomidine (). 相似文献
11.
Although the hydrochloride of -4--butyl-1-phenyl--1-(N-piperidyl)cyclohexane crystallizes in the conformation with axial -butyl, it exists as an almost equimolar mixture of the two chair conformers in CD2 Cl2 solution. The position of equilibrium allows one to calculate ΔG°-Bu as ?4.9 kcal/mol. 相似文献
12.
4-(N-Alkylimino)methyl-2,6-di--butylphenols (), Schiff bases of 3,5-di--butyl-4-hydroxybenzaldehyde can be oxygenated in the presence of Co(Salpr), a five coordinate Co(II)-Schiff base complex to give N-alkyl-3--butyl-5-formyl-2-hydroxy-2-pivaloyl-1,2-dihydropyridines ( as the main product together with 3-formyl-2,5-di--butyl-2,4-cyclopentadienone () and 2,6-di--butyl-4-formyl-6-hydroxy-4,5-epoxy-2-cyclohexenone (). These products result from dioxygen incorporation into the ortho position of . 相似文献
13.
Photoreaction of N-(ω-indol-3-ylalkyl)phthalimides ( and ) gave oxeto[2,3-b]indoles ( and ), the first example of oxetane formation of the aromatic imide carbonyl in the Paterno-Buchi reaction. 相似文献
14.
(R,R)-tartaric acid has been converted into (R,R)-dimethoxysuccinimide which after coupling with Z-3-hexenol and 5-hexynol followed by NaBH4/H⊕ reduction can be cyclised to optically pure and . 相似文献
15.
16.
The reaction of cesium fluoride with the 2-acyloxy 3-chloro 2-chloromethylpropanamides () gave the 3-acyloxy 3-chloromethyl azetidine 2-ones () . Treated by powdered potassium hydroxide, and were converted into the 1-oxa 4-oxo 5-aza spiro (2,3) hexanes. These reactions in heterogeneous media were very selective and gave excellent yields. 相似文献
17.
Separate optimized s and p bond functions (BFs) were added to the corresponding Dunning basis sets (11s,6p15s) → (5s,4p13s) for the four hydrides. Properties calculated with these basis sets are quasi-identical to those obtained with conventional polarization functions (dlp). The computer time ratios found are: t(BF)/t(dlp) = for UHF calculations, and for MC SCF calculations. 相似文献
18.
Yasuo Sakai Shingo Toyotani Yoshito Tobe Yoshinobu Odaira 《Tetrahedron letters》1979,20(40):3855-3856
Oxidative decarboxylation of [n.2.2]propellane carboxylic acids (-) with lead tetraacetate gave the bicyclic acetates (, ) having a bridgehead double bond and/or the tricyclic acetates (, ) in good yields. Vapor phase thermolysis of or afforded the bridgehead olefin or quantatively. 相似文献
19.
Stereospecific aldol condensation of at the bridge-head position with i-butyraldehyde gave and in a ratio of 4:1. Using the aldehyde the chiral centers were controlled to produce , in a ratio of 9:3:3:1. Deprotection of the major isomer afforded (±)-N,N′,O-trimethylbicyclomycin . 相似文献
20.
Nancy W. Withers W.C.M.C. Kokke Michel Rohmer W.H. Fenical Carl Djerassi 《Tetrahedron letters》1979,20(38):3605-3608
The sterol fraction of the cultured dinoflagellate contains in addition to cholesterol, 24-methylcholesterol, 4,24-dimethylcholesterol and dinosterol () small amounts of the cyclopropyl-containing sterols gorgosterol () and 5α-gorgostanol () as well as 4α-methylgorgostanol () and E-4α,22ξ,23ξ (or 24ξ)-trimethylcholest-17(20)-en-3β-ol ( or ). The biosynthetic implications of the first isolation of such sterols from a free-living alga are emphasized. 相似文献