Mária Kajtár-Peredy

An efficient synthesis of l-idose and l-iduronic acid thioglycosides and their use for the synthesis of heparin oligosaccharides

Efficient preparations of thioglycoside derivatives of L-idose and L-iduronic acid are described. The method avoids the tedious chromatographic separations of furanose and pyranose anomeric mixtures, and affords the thioglycosides in a stereoselective manner. The L-idose and L-iduronic acid thioglycosides having combinations of different protecting groups proved to be efficient glycosyl donors in the synthesis of heparin disaccharides.

Lipase-catalyzed enantiomer selective hydrolysis of 1,2-diol diacetates

Abstract Enantiomer selective hydrolysis of racemic 1,2-diol diacetates (rac-2a-h) was investigated by using the inexpensive commercial porcine pancreatic lipase. The hydrolysis proceeds with variable regioselectivity but with moderate to good enantioselectivity yielding a mixture of isomeric monoacetates (3a-h and 4a-h) and unchanged diacetate enantiomers (2a-h). Evidence was found that both monoacetates (3a-h and 4a-h) are formed with the same sense of enantiomer selectivity.

Total synthesis of plagiochins C and D, macrocyclic bis(bibenzyl) constituents of plagiochila acantophylla

Abstract Plagiochins C ( 3 ) and D ( 4 ) were synthesized by convergent schemes. Rings C and B were joined by Ullman ether synthesis, the arylaryl bond between rings A and D was formed by Pd(0)-catalysed coupling of an arylboronic acid (ring D) and a bromobenzoic ester (ring A). Rings C and D were linked by the Wittig reaction, while final ring closure was effected by tetraphenylethene assisted Wurtz reaction.

The synthesis of riccardin C

Abstract The macrocyclic bis(bibenzyl) riccardin C, isolated from Riccardia multifida was synthesized in an unambiguous way by Ni(O) assisted intramolecular aryl-aryl bond formation from a diiodobenzoate as the key step.

Total syntheses of riccardins A, B, and C, cytotoxic macrocyclic bis(bibenzyls) from liverworts

Di-O-methylriccardin A (3), riccardin A (1), and riccardin B (4) were synthesized by convergent schemes. Rings A and D of both riccardin A and B, as well as rings B and C of riccardin B were joined by the Ullmann ether synthesis. The aryl-aryl bond in riccardin A was established by Ni(0)-assisted intramolecular coupling of a di-iodoester (17). Rings A and B were linked in all syntheses by the Wittig reaction, whereas ring closure was effected by a tetraphenylethene catalyzed Wurtz reaction. Demethylation of (3) gave riccardin C (2).

Simple and condensed β-lactams. I: The application of diketene in β-lactam synthesis. The synthesis and functional group manipulations of diethyl 3-acetyl-4-oxoazetidine-2,2-dicarboxylates

Abstract Acylation of the N-substituted diethyl aminomalonates 3a – 3d with diketene furnished the ring tautomers 6a – 6d of the expected acetoacetyl derivatives 5 . By treatment with iodine and sodium ethoxide compounds 6a – 6d are smoothly converted into the β-lactam derivatives 2a – 2d . Deethoxycarbonylation of the ethylene ketals 7a – 7d of the latter furnishes mixtures of the corresponding diastereomeric monoesters 8 and 10 . The ethoxycarbonyl groups of the trans esters 8 are more reactive than those of the cis isomers 10 . This permits, under appropriate conditions, selective alkaline hydrolysis and NaBH 4 reduction of the trans esters 8 in the presence of the cis esters 10 . Reduction of the cis ester 10c under more forceful conditions furnishes the trans hydroxymethyl derivative 11c .

Synthesis of vinca alkaloids and related compounds. LXII: Synthesis of desmethoxy “decarbomethoxy apocuanzine”

Starting from the intermediate product (5) of the desmethoxy cuanzine synthesis, (±)-desmethoxy “decarbomethoxy apocuanzine” (4) was synthesized.

Simple and condensed β-lactams. Part 33. AlCl3 catalyzed ring closures of some 3-aryloxy-4-oxoazetidine-2-carboxylic chlorides to 1H-chromeno[3,2- b]azete-2,8(2aH,8aH)-diones and some reactions of the products

Abstract Carboxylic chlorides 3a–3c , when treated with AlCl 3 , afforded the tricyclic compounds 17a–17c . NaBH 4 reduction of 17a and 17b afforded compounds 11a and 11b . The latter and the related known compounds 4a, 5b, 6a and 7a were used for the preparation of various dihydrochromeno[3,2- b ]azet-2(1 H )-ones and of a 3,4-disubstituted chromane-2-carboxylic ester ( 26 ) of fixed stereochemistry. Catalytic reduction of 8-chloro compound 5b afforded compounds 10b and 25 , the products of simple hydrodechlorination and of azetidinone ring cleavage with concomitant hydrodechlorination, respectively.

Synthesis of vinca alkaloids and related compounds. LIII, A simple synthesis of (±)-3-oxovincadifformine and (±)-3-oxominovine

Starting from ethyl of 3- [5-ethyl-2-oxotetrahydro-1-pyridylethyl]indole-2-carboxylate synthese of the title compounds were achieved via linear reaction sequences

Unexpected reactions of (1R)2,3,4,6-tetra-O-acetyl-1-azido-D-galactopyranosyl cyanide and the derived carboxamide with triphenylphosphine

Abstract Staudinger reaction of acetylated (1 R )-1-azido-D-galactopyranosyl cyanide ( 1 ) with triphenylphosphine in diethyl ether led to the isolation of a crystalline phosphazide ( 2 ), unprecedented in carbohydrate chemistry. Spontaneous decomposition of 2 in toluene furnished the mixture of the unsaturated lactone 4 , as minor product, and two major products: the triphenylphosphoranylidene derivatives of (2 Z ,4 Z )-3-cyano-4,6-diacetoxy-2,4-hexadienoic amide ( 5 ), and (2 E ,4 Z )-triacetoxy-2,4-hexadienoic amide ( 6 ), respectively, owing to an unusual pyranoid ring opening between C-5 and the pyranose oxygen. The carboxamide analogue ( 10 ) of 1 underwent a regular phosphinimine formation affording the equilibrium mixture of both anomers 11 and 12 .