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).     

The benzhydryl ester of N-acetylneuraminic acid

Conclusions Benzhydryl protection of the carboxy group of N-acetylneuraminic acid has been described for the first time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1261–1262, July, 1966.     

Acylation of N-acetylneuraminic acid

Summary The direct acylation of N-acetylneuraminic acid takes place ambiguously and leads to two reaction products: the acylated -lactone and the acylated derivative of the pyranose form of the acid.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 2, pp. 191–197, 1967     

Glycosidation of N-acetylneuraminic acid

Conclusions The synthesis of the methyl esters of 9-O-(-D-glucopyranosyl)- and 9-O-(-D-galaetopyranosyl)-N-acetylneuraminic acid is described.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 215–217, January, 1968.     

Barbituric acid in the synthesis of fused 1,7-phenanthroline derivatives

New 7-aryl(hetaryl)-7,8,9,10,11,12-hexahydropyrimido[5,4-b][1,7]phenanthroline-9,11-diones have been synthesized by three-component condensation of barbituric acid with quinolin-5-amine and aromatic or heteroaromatic aldehydes.     

Novel synthesis of L-ribose from D-mannono-1,4-lactone

[reaction: see text] D-Mannono-1,4-lactone was efficiently converted into L-ribose in eight steps. A key step of this synthesis is the cyclization of a gamma-hydroxyalkoxamate under Mitsunobu conditions. It is noteworthy that the O-alkylation product was obtained in 94% yield and that none of the N-alkylation product was detected in this cyclization.     

A facile synthesis of natural products chaetomellic acid A and 1,7(Z)- nonadecadiene-2,3-dicarboxylic acid

Synthesis of recently isolated bioactive natural products chaetomellic acid A anhydride (1) and a novel 1,7(Z)-nonadecadiene-2,3-dicarboxylic acid (2) have been described. Chemoselective carbon[bond]carbon S(N)2' coupling reactions of appropriate Grignard reagents with dimethyl bromomethylfumarate (7) in diethyl ether in the presence of HMPA at room temperature furnished the corresponding diesters 8 and 15 in 60-62% yields. The formed diesters 8 and 15 on hydrolysis gave respectively the corresponding desired diacids 9 and 2 in quantitative yields. Acetic anhydride induced ring closure of diacids 9 and 2 respectively gave the chaetomellic acid A anhydride (1) and isochaetomellic acid B anhydride (16) with 38-39% overall yields in five steps.     

Enantioefficient synthesis of alpha-ergocryptine: first direct synthesis of (+)-lysergic acid

The first direct synthesis of (+)-lysergic acid (2a) suitable for scale-up has been achieved by the following reaction sequence. Bromoketones 4d or 4g were allowed to react with amine 5 followed by deprotection, and the resulting diketone 6c was transformed into the unsaturated ketone (+/-)-7 by the LiBr/Et(3)N system. Resolution afforded (+)-7, which was further transformed by Sch?llkopf's method into the mixture of esters 2e and 2f. Upon hydrolysis the latter mixture afforded (+)-2a. The peptide part of alpha-ergocryptine (1) was prepared according to the Sandoz method; the stereoefficiency, however, has been significantly improved by applying a new resolution method and recycling the undesired enantiomer. Coupling the peptide part with lysergic acid afforded 1. Having synthetic (+)-7 in hand, we can claim the total synthesis of all the alkaloids which were prepared earlier from (+)-7 that had been obtained through degradation of natural lysergic acid.     

A first synthesis of sulfonic acid analogues of N-acetylneuraminic acid

Sulfonic acid analogues of N-acetylneuraminic are synthesized from 1-thio-l-fucoside derivatives with the introduction of an azido group at C-4 of the fucose moiety and carbanionic addition onto fully protected lactones. The analogues in the form of methyl glycosides are subjected to a neuraminidase inhibition assay.     

Short and straightforward synthesis of 1,7-dimethyl-1,4,7,10-tetraazacyclododecane

A novel, cost-effective, and efficient process for the synthesis of 1,7-dimethyl-1,4,7,10-tetraazacyclododecane 1 has been developed. The two-step process involved the selective conversion of commercially available cyclen to N1,N7-diethylcarbamate cyclen 3 that afforded the title compound in high yield after the reduction step.     

The first synthesis of the benzo[b]indolo[1,2-h][1,7]naphthyridine ring system

The first syntheses of representatives of the benzo[b]indolo[1,2-h][1,7]naphthyridine ring system have been accomplished using the Friedländer reaction.     

Straightforward synthesis of 1,7-dioxaspiro[4.4]nonanes

The reaction of 2-chloromethyl-3-(2-methoxyethoxy)prop-1-ene with an excess of lithium powder and a catalytic amount of naphthalene (2.5%) in the presence of a carbonyl compound (E¹=R¹R²CO) in THF at −78 to 0 °C, followed by the addition of an epoxide [E²=R³R⁴C(O)CHR⁵] at 0 to 20 °C leads, after hydrolysis, to the expected methylidenic diols. These diols, in the presence of iodine and silver(I) oxide in dioxane-water, undergo double intramolecular iodoetherification to give the corresponding 1,7-dioxaspiro[4.4]nonanes, which in addition can be easily oxidised to a variety of 1,7-dioxaspiro[4.4]nonan-6-ones.     

Solid-phase synthesis of 1,7-disubstituted-1,3,5-triazepane-2,4-diones

[reaction: see text]. The solid-phase synthesis of 1,7-disubstituted-1,3,5-triazepane-2,4-diones from resin-bound amino acids is described. The exhaustive reduction of solid-support bound amides with borane afforded the requisite secondary amines, which following treatment with phenyl isocyanatoformate and cleavage, provided the corresponding triazepane-2,4-diones.     

Stereoselective synthesis of cis-p-menth-8-ene-1,7-diol, cis-p-menthane-1,7-diol, and cis-p-menthane-1,7,8-triol

The natural products cis-p-menthane-1,7-diol (cis-IV), cis-p-menth-8-ene-1,7-diol (cis-I) and cis-p-menthane-1,7,8-triol (cis-II) are obtained starting from the corresponding cis-cyanohydrins, cis-2 and cis-7, respectively, by chemical transformation of the cyano into the hydroxymethyl group. The key step of the synthesis is the very high cis-selectivity (> or = 96 %) of the MeHNL-catalyzed HCN addition to 4-alkylcyclohexanones. From 4-isopropylcyclohexanone (1) the cyanohydrin cis-2 and from 4-(1-methylvinyl)cyclohexanone (6) the cyanohydrin cis-7 result almost quantitatively. Regioselective hydroxylation of cis-I affords the triol cis-II. X-ray crystal structure determinations of the final products confirm their cis-configuration.     

The first synthesis of an epidiselenodiketopiperazine

Epidithiodiketopiperazines (ETPs) are natural products (e.g., gliotoxin) with varied and important biological activity, which often is attributed to the redox properties of the disulfide moiety. As such, analogs with altered redox properties and similar structural characteristics would be of value to biological investigations. The use of an ETP as the point of departure in the first synthesis of an epidiselenodiketopiperazine (ESeP) and its activity against Mycobacterium tuberculosis (MTB) is reported.     

The first synthesis of PEG-carotenoid conjugates

Carotenoid-PEG esters and diesters were synthesized from several carotenols with polyethyleneglycols of different chain length to enhance the water solubility and bioavailability of these hydrophobic carotenoids. The water solubility of the products was compared and found, as expected, to be proportional with the PEG content of the conjugates.