Application of the NG-(2,2,5,7,8-pentamethylchroman-6-sulphonyl) derivative of FMOC-arginine to peptide synthesis

The trifluoroacetic acid labile pentamethylchromanylsulphonyl protecting group for the guanidino group of arginine has been used in conjunction with the base-labile Fmoc Nα protecting group for the synthesis of arginine-containing peptides.     

Potassium 2,2,5,7,8-pentamethylchroman-6-oxide: a rationally designed base for Pd-catalysed amination

This base is just right! A new base, potassium 2,2,5,7,8-pentamethylchroman-6-oxide, for Pd-catalysed amination has been rationally designed that has sufficient basicity to efficiently deprotonate the intermediate aryl palladium ammonium complex, leading to far better rates than obtained with carbonate, which is known to be very mild. At the same time, this new base possesses minimal nucleophilicity to mitigate the degradation of base-sensitive functional groups in the starting materials and products, such as is commonly seen with potassium or sodium tert-butoxide.     

Phenyl-EDOTn derivatives as super acid labile carboxylic acid protecting groups for peptide synthesis

A series of new 3,4-ethylenedioxy-2-thenyl (EDOTn) derived alcohols have been synthesized and evaluated as super acid labile carboxylic acid protecting groups. All the derivatives are labile to very low concentrations of TFA (0.01-0.5%).     

Preparation and application of new acid labile anchor groups for the synthesis of peptide amides by FMOC solid phase synthesis

The synthesis and application of new linkage agents for the preparation of peptide amides using a modified Fmoc strategy is described.     

A new environment-sensitive fluorescent amino acid for Fmoc-based solid phase peptide synthesis

A new 4-(N,N-dimethylamino) phthalimide-based environment-sensitive fluorescent building block for solid phase peptide synthesis, has been synthesized and incorporated into peptides. Peptides incorporating this residue show great potential for biological applications in sensing protein/protein interactions.     

A new method for the synthesis of aldehyde-spacered oligosaccharides by oxidation of l-tartaric acid derivative

Russian Chemical Bulletin - N-(N-[(2R,3R)-2,3-Dihydroxy-3-carboxypropionyl]glycyl)-β-d-glycopyranosylamines and N-[N-(formylcarbonyl)glycyl]-β-d-glycopyranosylamines, derivatives of...     

Preparation of DL-N-benzyloxycarbonyl-gamma-carboxy-glutamic acid-gamma, gamma'-di-t-butyl-alpha-methyl ester, a suitable derivative for peptide synthesis with the new aminotricarboxylic acid from prothrombin]

The first synthesis of a selectively, fully protected derivative of the new aminotricarboxylic acid found in prothrombin and other homologous blood-clotting factors, γ-carboxy-glutamic acid (Gla), is described. The compound DL -N-benzyloxycarbonyl-γ-carboxy-glutamic acid γ,γ′-di-t-butyl-γ-methyl-ester is potentially useful for peptide synthesis. The free amino-acid (DL -Gla) and DL -pyro-γ-carboxy-glutamic acid dimethyl-ester were also prepared.     

A new ellagic acid derivative from Polygonum runcinatum

A new ellagic acid derivative, 3,3′-dimethylellagic acid-4′-O-(6″-galloyl)-β-d-glucoside, named runcinatside (5), together with four known compounds 3,3′-dimethylellagic acid (1), 3,3′,4′-trimethylellagic acid (2), 3,3′-dimethylellagic acid-4′-O-β-d-glucoside (3) and 3-methylellagic acid-4′-O-α-l-rhamno-pyranoside (4), was isolated from the roots of Polygonum runcinatum Buch.-Ham. ex D.Don Var. sinense Hemsl and the structures of these compounds were established by spectroscopic methods and comparison with previously reported data. All compounds showed antioxidant activities in vitro and compound 5 possessed the highest activity.     

A thieno-2H-chromene alpha-amino acid derivative: synthesis and photochromic properties

[structure: see text] A new photochromic thieno-2H-chromene alpha-amino acid derivative was prepared by C-N palladium-catalyzed cross-coupling of a bromothieno-2H-chromene with the aminated aromatic side chain of the methyl ester of a N,N-diprotected amino acid. Its good photochromic properties demonstrated by flash photolysis and continuous irradiation indicate a possible application in ophthalmic lenses. It may also be inserted into peptides to give photoinduced reversible structural changes.     

Enantioselective synthesis of valoneic acid derivative

The enantioselective synthesis of trimethyl octa-O-methylvaloneate (1) was accomplished using the Bringmann’s ‘lactone concept’, which involves the intramolecular biaryl coupling reaction of a phenyl benzoate derivative and the asymmetric lactone-opening reaction.     

A new synthesis of N-acetylneuraminic acid

A new synthesis of N-acetylneuraminic acid (Neu5Ac; 28 ) via aldehyde 10 is described. The aldehyde 10 was obtained from N, acetyl-D -glucosamine ( 11 ; 5 steps, overall yield ca. 6%) or from D-glucono-1,5-lactone ( 17 ; 6 steps, overll yield ca 57%). Thus, on the one hand, N-acetyl-D -mannosamine ( 12 ), obtained from 11 , was transformed into the known dithioacetal 14 and hence into the (ethylthio)dihydrooxazole 16 , which was cleaved under weakly acidic conditions to the aldehyde 10 . On the other hand, the known ester 18 , obtained from 17 , was sulfonylated and further transformed via the azide 20 into the N-acetyl-D -mannonate 22 . Reduction of 22 to 23 and oxidation of 23 with ‘periodinane’ again gave 10 . The aldehyde 10 was treated with the organozinc reagent 8 obtained from tert-butyl 2-(bromomethyl)acrylate ( 2 ) to yield predominantly 24 , which was transformed (two steps) into the 2-methylidene-D -glycero-nononic acid 27 and hence into Neu5Ac (28).     

A new synthesis of lysergic acid

[reaction: see text] (+/-)-Lysergic acid has been synthesized via an economical 8-step route from 4-bromoindole and isocinchomeronic acid without the need to protect the indole during the synthesis. Initial efforts to form the simpler 3-acylindole derivatives first and then cyclize these were unsuccessful in the cyclization step.     

α-(Phenylacetamido)benzylpolystyrene (pab-resin) : A new polymeric support for peptide synthesis with improved acid stability

Solid phase peptide synthesis carried out on conventional chloromethyl polystyrene support has the disadvantage of the acidolysis of the peptide-resin linkage during the deprotection step. In addition, when trifluoroacetic acid is used as deprotecting agent, intrapolymeric trifluoroacetyl transfer may give rise to truncated trifluoroacetylated peptides. A new polymer support devised to minimize these problems, α - (4 - chloromethyl-phenylacetamido) benzylcopoly(styrene-1%-divinylbenzene) (ClCH₂-Pab-resin), has been synthesized. The acetamido bridge between the peptide and the resin increases the acid stability of the new support thus allowing the synthesis of purer peptides in higher yields. Boc-aminoacyl-OCH₂-Pab-resins can be readily prepared in a versatile way by reaction of Boc-amino acid caesium salts with chloromethyl-Pab-resin. This fact contrasts with the rather elaborate procedures required for previously described similar resins.The synthetic viability of the chloromethyl-Pab-resin is shown by the synthesis of Ac-His-Arg-Tyr-Arg-Pro-OH (fragment 39–43 of histone H3). The synthesis and subsequent purification are exhaustively compared with the parallel synthesis carried out on a standard chloromethyl polystyrene support. The presence of the acetamido linkage provokes, as expected, a decrease in the HF cleavage yield. Nevertheless, this disadvantage is balanced by the increase in global purification yields even for the synthesis of a pentapeptide for which only five deprotection steps are required.     

A new method for the synthesis of levulinic acid

A two- step method is described for the synthesis of levulinic acid from ethyl acetoacetate and ethyl chloroacetate in 70% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 474–475, February, 1990.