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1.
A new aminocyclitol derived from bicyclo[4.2.01,6]octane was synthesized starting from cyclooctatetraene. Photooxygenation of trans-7,8-diacetoxy-bicyclo[4.2.0]octa-2,4-diene afforded a bicyclic endoperoxide. Reduction of the endoperoxide with thiourea followed by a palladium-catalyzed ionization/cyclization reaction gave an oxazolidinone derivative. Oxidation of the double bond in the oxazolidinone with KMnO4 followed by acetylation gave the oxazolidinone-tetraacetate whose exact configuration was determined by X-ray diffraction analysis. Hydrolysis of the oxazolidinone ring and removal of the acetate groups furnished the desired aminocyclitol. 相似文献
2.
Raman spectroscopic studies of dl-serine and dl-valine under static high pressures have been carried out up to 8 and 7 GPa, respectively to understand the behaviour of hydrogen bonds in these compounds. The discontinuous changes in the pressure dependence of some of the Raman modes of dl-serine at 1.5 GPa are interpreted to be due to molecular rearrangements brought about by changes in the hydrogen bonding interactions. Our results of the pressure dependence of N–H?O librational modes in dl-valine at 3 GPa suggest changes in the nature of hydrogen bonding interactions across this pressure. 相似文献
3.
A key intermediate corresponding to a rare sugar framework has been synthesized, starting from d-xylose, an inexpensive carbohydrate. This approach gave access to new elaborated sugar moieties for structure–activity relationships in the KRN research. 相似文献
4.
Chaitali Chakraborty 《Tetrahedron》2007,63(48):11984-11990
Diastereo- and regioselelective intra-molecular nitrone-olefin cycloaddition reaction of in situ generated N-benzylnitrones, obtained from d-glucose derived precursors 5a/5b furnished dihydroxy functionalized isoxazolidines. The N-O bond reductive cleavage and removal of N/O-benzyl groups led to the formation of stereochemically well defined aminocyclohexitols. 相似文献
5.
Gagik G Melikyan Steve Sepanian Ferdinand Villena Brian Ahrens John Matchett Edwin Abrenica Kenneth I Hardcastle 《Journal of organometallic chemistry》2003,683(2):324-330
The highly stereoselective synthesis of d,l-hexestrol (1), an inhibitor of microtubule assembly, is developed by using, as a key step, an intermolecular coupling of Co2(CO)6-complexed propargyl radicals. The latter are generated by novel complementary processes involving an interaction of tetrahydrofuran with Co2(CO)6-complexed propargyl alcohols and cations. An isomerically pure d,l-μ-η2-[3,4-di(4-methoxyphenyl)-1,5-hexadiyne]-bis-dicobalthexacarbonyl (d,l-6) is isolated in 69-91% yield with intermolecular coupling reactions exhibiting an excellent chemo- (0.5-7%) and d,l-diastereoselectivity (90-94%). The structure of d,l-6 is determined by X-ray diffraction. The subsequent steps include BBr3-induced demethylation of 4-methoxyaryl groups, demetalation with cerium(IV) ammonium nitrate, and hydrogenation of acetylenic termini affording d,l-hexestrol (1). 相似文献
6.
Eder José Guidelli Ana Paula RamosMaria Elisabete D. Zaniquelli Patricia NicolucciOswaldo Baffa 《Radiation Physics and Chemistry》2012,81(3):301-307
The potential use of alanine for the production of nanoparticles is presented here for the first time. Silver nanoparticles were synthesized using a simple green method, namely the thermal treatment of silver nitrate aqueous solutions with dl-alanine. The latter compound was employed both as a reducing and a capping agent. Particles with average size equal to 7.5 nm, face-centered cubic crystalline structure, narrow size distribution, and spherical shape were obtained. Interaction between the silver ions present on the surface of the nanoparticles and the amine group of the dl-alanine molecule seems to be responsible for reduction of the silver ions and for the stability of the colloid. The bio-hybrid nano-composite was used as an ESR dosimeter. The amount of silver nanoparticles in the nanocomposite was not sufficient to cause considerable loss of tissue equivalency. Moreover, the samples containing nanoparticles presented increased sensitivity and reduced energetic dependence as compared with pure dl-alanine, contributing to the construction of small-sized dosimeters. 相似文献
7.
We have prepared an l-tyrosine derivative bearing a d-threo ketose moiety by a convenient chemoenzymatic route. This compound is of potential interest for developing stereospecific assays for enzymes catalyzing C-C bond cleavage such as transketolase. We showed in vitro by analytical studies (LC/MS and 31P NMR) that this compound can release l-tyrosine in the presence of wild type TK extract and bovine serum albumin. This assay is the first step towards a mutant TK selection test that could be developed for yeast cells auxotrophic for l-tyrosine. 相似文献
8.
An efficient method for the stereoselective synthesis of l-ribose was accomplished starting from commercially inexpensive d-fructose. The intermediates in the process can serve as versatile precursors for the preparation of l-nucleoside analogues. 相似文献
9.
The enzymatic synthesis of Z-l-aminoacyl-l-caprolactam amides from Z-protected amino acid esters and dl-α-amino-ε-caprolactam (ACL) was accomplished by the thiol proteases papain, bromelain and ficin in aqueous-organic media. Product yields of 96% and 87% for Z-Gly-l-ACL and Z-Ala-l-ACL, respectively, could be obtained. The products were purified and characterised by polarimetry, NMR and LC-MS. The suitability to accept a bulky 1,2-amino ketone as a nucleophile expands the general knowledge of thiol proteases and their catalytic potential. 相似文献
10.
Xuequan Lu 《Tetrahedron letters》2005,46(18):3165-3168
The preparations of d-ribo- and l-lyxo-phytosphingosines (1, 2) are described. Chelation-controlled addition of tetradecylmagnesium bromide to pentylidene-protected d-threitol aldehyde 6 afforded the key intermediate tetrol 7, providing the desired l-lyxo stereochemistry of phytosphingosine. Inversion at C4 of intermediate 7 provided the d-ribo stereochemistry. 相似文献
11.
A preparative and short synthesis of l-ribose and l-apiose was accomplished starting from d-ribose via stereoselective cis-dihydroxylation and C2-hydroxymethylation, respectively. These l-sugars can serve as versatile intermediates for the synthesis of l-nucleosides. 相似文献
12.
Racemic oleandrose (2,6-dideoxy-3-O-methyl-arabino-hexone) has been obtained starting from the Diels-Alder adduct between 4-methoxy-3-buten-2-one and isobutyl vinyl ether, which was converted into a mixture of the isobutyl β- and α-oleandrosides through hydroboration-oxidation. The latter reaction is highly diastereoselective since attack by borane takes place exclusively anti to the OMe group: none of the diasteroisomeric cymarosides are formed. The only side-products are small amounts of the isobutyl β- and α-amicetodies formed by a demthoxylation occuring during the hydroboration step. 相似文献
13.
《Tetrahedron letters》2003,44(19):3771-3773
l-Isonucleosides 17 and 19 were stereoselectively synthesised from (S)-glycidol by two different procedures. The key step was the synthesis of a chiral dihydrofuran which was carried out by oxidation/elimination of 8 and by ring-closing metathesis of diene 10. The procedure can be applied to the synthesis of both enantiomers. 相似文献
14.
Takahiro Ohishi Hirokazu Nanba Masashi Izumida Kohei Mori Makoto Ueda Kenji Inoue 《Tetrahedron letters》2007,48(19):3437-3440
A scalable and cost-effective synthesis of d- and l-α-methylcysteine is described. A key step is d-selective cyclization of N-carbamoyl S-tert-butyl-d,l-α-methylcysteine catalyzed by hydantoinase. d-5-tert-Butylthiomethyl-5-methylhydantoin and N-carbamoyl S-tert-butyl-l-α-methylcysteine were obtained with excellent yield and optical purity, and these compounds were easily separated by filtration. After hydrolysis and cleavage of the tert-butyl group, d- and l-α-methylcysteine hydrochloride were obtained. 相似文献
15.
Carrie L.K. Gilbert 《Tetrahedron》2005,61(35):8339-8344
l,l-Puromycin, a diastereomer of the natural peptidyl nucleoside antibiotic puromycin, has been synthesized from l-xylose in 13 steps. 相似文献
16.
Starting from a single suitable functionalised epoxide, a highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine is described. The approach allows the formal preparation of all stereoisomers of these sphingoid structures. 相似文献
17.
Regio- and stereoselective cycloaddition of methyl acrylate to C-glycosyl nitrones derived from d-galactose and d-glucose, giving 5-methoxycarbonyl-3-(pentoglycos-5-yl or pentitol-1-yl)isoxazolidines, is reported. Transformation of one of them into a 4-hydroxy-2-(pentoglycos-5-yl)pyrrolidine derivative, potentially useful in a route to polyhydroxy-perhydroazaazulenes, was achieved. 相似文献
18.
Manuel Friedel 《Tetrahedron letters》2004,45(13):2779-2781
A short synthesis of l-aminohomohistidine (l-Ahh), which starts from readily available δ-hydroxy-l-lysine is described. The embedding of the basic guanidino moiety in the aromatic imidazole lowers the basicity of the side chain to a pKa of 8.3. It is proposed that l-Ahh may be employed as an arginine-mimetic in medicinal chemistry. 相似文献
19.
Two sulfur-containing amino acids, dl-cysteine (Cys) and dl-penicillamine (PenA), were condensed with ninhydrin to form their spirothiazolidine derivatives. These were separated by HPLC using α-acid glycoprotein (AGP) and β-cyclodextrin (β-CD) columns. The resolution conditions were optimized and the results were compared. Since the method provided resolution greater than 2 it was also applied to preparative separation. After separation, each of them was detagged using Zn dust and 10% aqueous trifluoroacetic acid. For analytical purposes dinitrophenyl (DNP) derivatives of dl-Cys and dl-PenA were also prepared and were resolved on both the columns. The detection was carried out using photodiode array detection system at 231 nm. The limits of detection were found to be 0.01% and 0.004% for spirothiazolidine carboxylic acid and DNP derivatives, respectively. 相似文献
20.
Alexander C. Weymouth-Wilson Daniel Best Maria-Soledad Pino-González 《Tetrahedron letters》2009,50(46):6307-5837
1,2-O-Isopropylidene-α-l-glucurono-3,6-lactone may be synthesized on a 100-200 g scale from cheaply available d-glucoheptonolactone in an overall yield of 94% in four steps via l-glucuronolactone. Subsequent elaboration to l-glucose, diacetone-l-glucose (1,2:5,6-di-O-isopropylidene-α-l-glucofuranose), and monoacetone-l-glucose (1,2-O-isopropylidene-α-l-glucofuranose) allows easy access to a range of l-sugar chirons. 相似文献