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Plant diseases caused by bacteria lead to enormous yield and economic losses in agricultural production. To develop innovative bactericides for controlling plant disease, a series of coumarin-3-carboxylic acid derivatives containing acylhydrazone thioether/sulfoxide were designed and synthesized by utilizing the principles of bioisosterism and active splicing. The bactericidal activities of these derivatives were subsequently evaluated. The result indicated that E2 exhibited the highest antibacterial activities in vitro against Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Acidovorax citrulli, with EC50 values of 2.97, 1.17, and 1.23 µg/mL, respectively. Moreover, in vivo experiments showed that E2 exhibited robust protective properties against Ralstonia solanacearum, and Acidovorax citrulli, with efficacies of 72.52 % and 63.90 %, respectively, at a concentration of 100 µg/mL, which was comparable to the positive control kasugamycin at the same concentration. Scanning electron microscopy analysis revealed that E2 induced changes in the cellular morphology of Acidovorax citrulli, such as shrinkage and collapse. Subsequent investigation revealed that E2 had the capacity to compromise the structural stability of the bacterial membrane of Ralstonia solanacearum. This study represents the first report on the antibacterial activities of this series of coumarin-3-carboxylic acid derivatives containing the acylhydrazone thioether/single-sulfoxide moiety, and the results suggest that coumarin-3-carboxylic acid derivatives containing the acylhydrazone single-sulfoxide may hold potential as effective antibacterial agents. And coumarin-3-carboxylic acid derivatives exhibited promise as plant bacterial agent to prevent rice bacterial leaf blight, tomato bacterial wilt, and melon bacterial fruit blotch.

In this paper, a practical approach for the total synthesis of kipukasin A is presented with 22% overall yield by using tetra-O-acetyl-β-D-ribose as starting material. An improved iodine-promoted acetonide-forming reaction was developed to access 1,2-O-isopropylidene-α-D-ribofuranose. For the first time, ortho-alkynylbenzoate was used as protecting group for the 5-hydoxy group. After subsequent Vorbrüggen glycosylation, the protecting group could be removed smoothly in the presence of 5 mol % Ph3PAuOTf in dichloromethane to provide kipukasin A in high yield and regioselectivity.

The first total synthesis of 5′-O-α-d-glucopyranosyl tubercidin was successfully developed. It is a structurally unique disaccharide 7-deazapurine nucleoside exhibiting fungicidal activity, and was isolated from blue-green algae. The total synthesis was accomplished in eight steps with 27% overall yield from commercially available 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d-ribose. The key step involves stereoselective α-O-glycosylation of the corresponding 7-bromo-6-chloro-2′,3′-O-isopropylidene-β-d-tubercidin with 2,3,4,6-tetra-O-benzyl-glucopyranosyl trichloroacetimidate. All spectra are in accordance with the reported data for natural 5′-O-α-d-glucopyranosyl tubercidin. Meanwhile, 5′-O-β-d-glucopyranosyl tubercidin was also prepared using the same strategy.

We report the first total synthesis of trachycladines A (10 steps, 34.2% overall yield) and B (11 steps, 35.0% overall yield) by using 5-deoxy-1,2,3-tri-O-acetyl-β-D-ribofuranose as the starting material. The critical step was the SnCl4 assisted regio- and steroselective deprotection of perbenzylated 1-O-methyl-5-deoxyribofuranose. The enzyme adenylate deaminase (EC 3.5.4.6) was successfully applied to the chemoenzymatic synthesis of trachycladines B.

Difficult-to-access 4-bromo quinolines are constructed directly from easily prepared ortho-propynol phenyl azides using TMSBr as acid-promoter. The cascade transformation performs smoothly to generate desired products in moderate to excellent yields with good functional groups compatibility. Notably, TMSBr not only acted as an acid-promoter to initiate the reaction, and also as a nucleophile. In addition, 4-bromo quinolines as key intermediates could further undergo the coupling reactions or nucleophilic reactions to provide a variety of functionalized compounds with molecular diversity at C4 position of quinolines.

An efficient approach for the synthesis of phosphorylated isoindoline fused with triazoles via Zn(OTf)2-catalyzed cascade cyclization of easily prepared ortho−propynol benzyl azides and diarylphosphine oxides is developed. The transformation occurred smoothly in moderate to excellent yields and tolerated various propargylic alcohol substrates.

The first total synthesis of the marine nucleoside Mycalisine B—a naturally occurring and structurally distinct 4,5-unsaturated 7-deazapurine nucleoside—has been accomplished in 10 linear steps with 27.5% overall yield from commercially available 1,2,3,5-tetra-O-acetyl-ribose and tetracyanoethylene. Key steps of the approach include: (1) I2 catalyzed acetonide formation from 1,2,3,5-tetra-O-acetylribose and acetone at large scale; (2) Vorbrüggen glycosylation using N4-benzoyl-5-cyano-6-bromo-7H-pyrrolo[2,3–d]pyrimidine as a nucleobase to avoid formation of N-3 isomer; (3) mild and scalable reaction conditions.

In the present paper, we report an efficient total synthesis of a marine alkaloid, rigidin E. The key tetrasubstituted 2-amino-3-carboxamidepyrrole intermediate was synthesized by cascade Michael addition/intramolecular cyclization between N-(2-(4-(benzyloxy)phenyl)-2-oxoethyl)methanesulfonamide and 3-(4-(benzyloxy)phenyl)-2-cyano-N-methylacrylamide. Subsequent carbonylation with triphosgene catalyzed by I2 and deprotection of benzyl groups afforded rigidin E in 21% overall yield. This strategy has the merits of metal-free reactions, low cost, mild reaction protocols, and easy access to diversity-oriented derivatives for potential structure-activity relationship investigation.

4-Amino-7-(5′-deoxy-β-d-xylofuranosyl)-5-iodo-pyrrolo[2,3-d]pyrimidine 1, an unusual naturally occurring marine nucleoside isolated from an ascidan, Diplosoma sp., was synthesized from d-xylose in seven steps with 28% overall yield on 10 g scale. The key step was Vorbrüggen glycosylation of 5-iodo-pyrrolo[2,3-d]pyrimidine with 5-deoxy-1, 2-O-diacetyl-3-O-benzoyl-d-xylofuranose. Its absolute configuration was confirmed.

In present paper, an expeditious total synthesis of naturally occurring 5′-deoxytoyocamycin and 5′-deoxysangivamycin was accomplished. Because of the introduction of a benzoyl group at N-6 of 4-amino-5-cyano-6-bromo-pyrrolo[2,3-d]pyrimidine, a Vorbrüggen glycosylation with 1,2,3-tri-O-acetyl-5-deoxy-β-D-ribofuranose afforded a completely regioselective N-9 glycosylation product, which is unambiguously confirmed by X-ray diffraction analysis. All of the involved intermediates were well characterized by various spectra.

In the present paper, we report an expedient total synthesis of triciribine, a tricyclic 7-deazapurine nucleoside and protein kinase B (AKT) inhibitor, in 35% overall yield. Our synthesis route features a highly regioselective substitution of 1-N-Boc-2-methylhydrazine and a trifluoroacetic acid catalyzed one-pot transformation which combined the deprotection of the tert-butylcarbonyl (Boc) group and ring closure reaction together to give a tricyclic nucleobase motif. [ABSTRACT FROM AUTHOR]

A glucopyranosyltriazole unit covalently bonded to a uridine nucleoside was synthesized and its gelation properties evaluated in ionic liquids. The ionogels were thermally stable; no melting occurred up to 111°C at 5wt% concentration. Moreover, ionogel formed by gelator at 3wt% concentration in [BMIM][TFSA] was found to retain the high conducting performances of the ionic liquid. [ABSTRACT FROM AUTHOR]

An efficient and practical synthesis of naturally occurring marine nucleosides 5′oxytubercidins on a 10 gram scale in good overall yield is reported. The key step was the Vorbrüggen glycosylation of pyrrolo[2,3-d]pyrimidines with 5-deoxy-1,2,3-tri- O-acetyl-b-D-ribofuranose. [ABSTRACT FROM AUTHOR]

A series of novel 1'-O-a-methyl isonucleosides were efficiently and stereoselectively synthesized with 1,2,3,5-tetra-Oacetyl-D-ribofuranose as the starting material. The key steps include regioselective and stereoselective deprotection of the 2,4-dichlorobenzyl group at C2, triflation, and substitution with appropriate nucleobases using cesium carbonate as the base. Removal of the residual 2,4-dichlorobenzyl groups and subsequent transformation afforded the title compounds in 30-37% overall yield. The products represent a new type of isonucleosides with 1'-O-substitution. [ABSTRACT FROM AUTHOR]