The synthesis of selectively protected β-diketones and α-ketoaldehydes

The reaction of acyl cyanides with enol silyl ethers produces β-cyano, β-hydroxy carbonyl compounds.     

Stereoselective synthesis of partially protected azasugar derivatives

Five-membered azasugar derivatives with partially protected hydroxyl groups, and their fluorinated derivatives were synthesized via the key intermediates of norbornyl-like bicyclic acetals using d-xylose and d-glucose as starting materials. The glycosylation of the azasugar intermediate and 1-methylenesugar was also explored. Translated from Chemical Journal of Chinese Universities, 2006, 27 (4) (in Chinese)     

Selectively protected galactose derivatives for the synthesis of branched oligosaccharides

Synthesis and characterization of several new anomerically pure galactose derivatives, based on simple and effective protective group manipulations of benzyl β-d-galactopyranoside, are reported. The monosaccharides described contain selectively protected/deprotected hydroxyl functionalities at their 1,2,3,4- and 6-positions rendering them useful as building blocks for construction of branched oligosaccharides.     

Preparation of bis(beta-trimethylsilylethanesulfonyl)imide and its use in the synthesis of protected amine derivatives

Bis(beta-trimethylsilylethanesulfonyl)imide (SES(2)NH) can be easily prepared in 85% yield by alkylation of the trianion of bismethanesulfonimide with 2 equiv of commerically available (iodomethyl)trimethylsilane. This synthon undergoes effective Mitsunobu alkylation reactions with both primary and secondary alcohols to afford the corresponding bis-SES imides. These imides can be selectively cleaved to the mono-SES-protected amines, and in addition undergo a one-pot cleavage/N-alkylation to afford SES derivatives of secondary amines.     

A short asymmetric total synthesis of chloramphenicol using a selectively protected 1,2-diol

A general route for the synthesis of chloramphenicol, thiamphenicol and fluoramphenicol is described. Chloramphenicol has been synthesized in 45% overall yield.     

The synthesis of malonimide derivatives as potential penicillin analogs

Malonimidoacetic acid derivatives (VIII, XIII) were synthesized as a potential penicillin analogs, hut they failed to inhibit the growth of bacteria when tested in vitro against a range of Gram-positive and Gram-negative microorganisms.     

A short diastereoselective synthesis of orthogonally protected diaminosuccinic acid derivatives

Homogeneous, Rh-catalyzed hydrogenation of heteromeric olefinic glycine dimers presents an efficient route to diastereomerically pure, orthogonally protected diaminosuccinic acid derivatives depending on the double bond geometry of the starting material. The products were obtained as racemates.     

Design and synthesis of cluster neoglycoconjugates based on D-glucose

Synthetic approaches have been developed to tetravalent neoglycoconjugates with different structures of the hydrophobic fragment and D-glucose fragment as branching core. The syntheses have been accomplished by preparation of blocks with terminal C≡C triple bonds and hydrophobic fragment and hydrophilic component (lactose derivative), followed by their conjugation.     

1,3,2-Oxazaphosphinane analogs of phosphorylacetic acid derivatives: synthesis and properties

Reactions of 2-AlkO-1,3,2-oxazaphosphinanes with alkyl N-haloacetylamino or N-chloromethyl-N-methoxycarbonylamino carboxylates mainly give products with retention (Alk = Me) and opening of the ring (Alk = Et). In aqueous solution, cyclic products with the N-isopropyl group are only stable, while the rest undergo hydrolysis with cleavage of the P-N bond of the ring. Oxazaphosphinane analogs of phosphorylacetamide and phosphorylacetohydrazide were synthesized.     

Indole-2,3-quinodimethanes : Synthesis of selectively protected derivatives of the fused dimeric indole alkaloid staurosporinone

The imine 1 was converted via an indole-2,3-quinodimethane cyclization to the hexahydroindolocarbazole 7, which was further converted to the N-carbomethoxy derivative of staurosporinone 2.     

Straightforward synthesis of orthogonally protected piperidin-3-ylmethanamine and piperidin-4-ylmethanamine derivatives

The 1,3- and 1,4-disubstituted piperidines are important building blocks in medicinal chemistry and drug discovery. We present the synthesis of orthogonally protected piperidin-3-ylmethanamine and piperidin-4-ylmethanamine derivatives from commercially available nipecotamide, isonipecotamide, nipecotic acid and isonipecotic acid. This is a straightforward two-step procedure that gives high overall yields. Purification of the intermediates using this procedure is not necessary, and the final compounds are purified by simple flash column chromatography.     

Stereospecific synthesis of urea-tethered neoglycoconjugates starting from glucopyranosyl carbamates

Silyl-assisted elimination reaction of glucopyranosyl carbamates has been established for the synthesis of α- and β-d-glucopyranosyl isocyanates and ureas. This method proved to be useful for the synthesis of urea-tethered neoglycoconjugates.     

Enzymatic synthesis of tryptamine and its halogen derivatives selectively labeled with hydrogen isotopes

Nine isotopomers of tryptamine and its halogen derivatives, labeled with deuterium, tritium in side chain, i.e., [(1R)-²H]-, [(1R)-³H]-, 5-F-[(1R)-²H]-, 5-F-[(1R)-³H]-, 5-Br-[(1R)-²H]-, double labeled [(1R)-²H/³H]-, 5-F-[(1R)-²H/³H]-, and ring labeled [4-²H]-, and [5-²H]-tryptamine, were obtained by enzymatic decarboxylation of l-Trp and its appropriate derivatives in deuteriated or tritiated media, respectively. Intermediates: [5′-²H]-l-Trp used for further decarboxylation was synthesized by enzymatic coupling of [5-²H]-indole with S-methyl-l-cysteine, and [4′-²H]-l-Trp was obtained by isotope exchange ¹H/²H of the authentic l-Trp dissolved in heavy water induced by UV-irradiation. Doubly labeled [(1R)-²H/³H]- and 5-F-[(1R)-²H/³H]-tryptamine were obtain by decarboxylation of l-Trp or [5′-F]-l-Trp carried out in ²H³HO incubation medium.     

Preparation of trimethylsilyl derivatives of amino acids and peptides for peptide synthesis

Russian Chemical Bulletin -     

A short and economical synthesis of orthogonally protected C-linked 2-deoxy-2-acetamido-alpha-D-galactopyranose derivatives

A short and high-yielding synthesis has been devised to prepare C-linked 2-deoxy-2-acetamido-alpha-D-galactopyranose derivative 3. One of the main advantages of this approach is that it employs commercially available and inexpensive d-glucosamine as the starting material. The key steps include a highly stereoselective C-allylation followed by epimerization of the C-4 hydroxyl group. Building block 3 and orthogonally protected C-linked 2-deoxy-2-acetamido-alpha-D-galactopyranose derivative 2 were obtained in 44% overall yield (six steps) and 29% overall yield (eight steps), respectively. This represents a significant improvement over previously reported syntheses.     

Preparation of C8-amine and acetylamine adducts of 2'-deoxyguanosine suitably protected for DNA synthesis

[reaction: see text] C8-Amine and acetylamine adducts of 2'-deoxyguanosine were synthesized. Our approach provides solutions for the coupling of aromatic amines to a protected 8-bromo-2'-deoxyguanosine derivative, for the selective acetylation of the coupled adduct at N(8) and for a protecting group scheme preserving the integrity of the base-labile N(8) acetyl group during DNA synthesis.