In this study, the target eight-membered iminosugars were constructed in one pot via [2 + 2] cycloaddition between the key enamine and alkyne moieties, followed by ring expansion, using amines, sugars bearing easily cleavable protecting groups at the terminal position, and butynoate esters as starting materials. This work provides a convenient skeletal editing strategy for the synthesis of uncommon eight-membered nitrogen-containing heterocycles.

A one-pot approach was developed for the direct synthesis of novel benzooxepino-fused tetrahydroquinoline-fused iminosugars via an intramolecular aza-Diels-Alder reaction mediated by an aryl iminium ion. The obtained multicyclic fused iminosugars were evaluated for their inhibitory activity against α- and β-glucosidases. The results showed that the iminosugars derived from l-ribose demonstrated significantly inhibitive activity against α-glucosidase, with IC50 values ranging from 2.77 μM to 6.12 μM. Kinetic analyses based on Lineweaver-Burk plots (1/V versus 1/[S]) indicated that compounds 3ba and 3bd act as rare uncompetitive inhibitors against α-glucosidase, with calculated Ki values of 10.50 ± 0.35 μM and 9.28 ± 0.31 μM, respectively.

In this study, the target eight-membered iminosugars were constructed in one pot via [2 + 2] cycloaddition between the key enamine and alkyne moieties, followed by ring expansion, using amines, sugars bearing easily cleavable protecting groups at the terminal position, and butynoate esters as starting materials. This work provides a convenient skeletal editing strategy for the synthesis of uncommon eight-membered nitrogen-containing heterocycles.

A series of diverse 2,3-dihydroquinazolin-4(1 H )-one- or imidazolidin-4-one-fused iminosugars were synthesized under different acid/base conditions, via a key iminium ion derived from Ts/Ms-activated saccharides and aminoamide derivatives.

A series of semi-saturated fused polycyclic iminosugars were synthesized by one-pot stereoselective three-component reactions of D-ribose tosylate, aniline and cycloenones under heating conditions. The N-aryl enamine derived from an iminium ion is the key intermediate for the reaction. In this way, various novel complex fused iminosugars were obtained through a normal Diels-Alder mechanism at 80 degrees C. This strategy will enable the preparation of bioactive iminosugar analogues with structural diversity.

A metal‐free method is developed for the synthesis of N‐arylated lactam‐type iminosugars using hydrogen peroxide (35% in water) as an oxidant. The reaction of various α‐amino carbonyl compounds is performed in methanol, and the active methylene adjacent to the carbonyl group is rapidly removed to form a carboxylic acid as the key intermediate through a cascade radical cleavage reaction. Following an intramolecular amidation reaction, a series of N‐arylated lactam‐type iminosugars are prepared in satisfactory yields, providing an alternative protocol for the synthesis of such bioactive iminosugars. Additionally, several 4‐aminobutanamide derivatives are obtained by intermolecular amidation of the carboxylic acid intermediate.

A simple and effective synthesis method has been developed through Mannich and transannular reaction mechanisms to convert iminosugar C-coumarinyl glycosides 4a into cis-bicyclic γ-lactam derivatives 8a. The adaptability of this method has been demonstrated through various substituted coumarins, tosylated sugars, and amines. The extension reaction proved the plasticity of the bicyclic skeleton. In addition, this reaction has the characteristics of simple operation, a high yield, and high atomic economy.

Ni(OTf)2-Catalyzed C-glycosylation was described herein for the convenient preparation of iminosugar C-nucleosides using N-methyl 3-aminopyrazole and tosylated sugars as the starting materials. The method provided an efficient route for constructing iminosugar C-nucleoside with low cost.

In the presence of Hantzsch ester and with JohnPhosAuCl/AgOMs as catalysts, a series of indole-fused iminosugars were obtained in good yields by the intramolecular reductive coupling reaction of iminosugar C-glycoside, in which the terminal alkyne could be coupled with indole and further reduced to methyl. The substrates of iminosugar C-glycosides were conveniently prepared by a three-component reaction of tosylated/mesylated sugar, propargylamine, and indole derivatives. The advantages of this protocol are its simplicity and efficiency in constructing the complex indole-fused iminosugars.

HCl-catalyzed C-glycosylation was described herein for the convenient preparation of N-heteroaryl C-glycosides and polyhydroxylated alkanes with diaryl groups using hetereoaryl amines and unprotected sugars as starting materials. The reaction temperature and the amounts of aryl amines and HCl had significant effects on reactions. The method provided a highly efficient and environmentally friendly route for constructing C-glycosides at low cost.

This study presents the synthesis of novel naphthofurano-iminosugars (4) using 2,3-O-isopropylidene D-ribose tosylate (1a), anilines (2), and 1,4-benzoquinone (3a) as starting materials through key iminium ion/enamine intermediates via [3 + 2] cyclization reactions at room temperature. The reaction has unique regioselectivity and stereoselectivity with moderate to excellent yields. The adaptability of this method has been demonstrated using various substituted anilines, on which both electron-donating and electron-withdrawing groups were well employed in the reactions. Notably, the treatment of the fused multicyclic iminosugar 4 with TFA efficiently leads to an interesting unexpected pyridinium salt (8), possible via four sequential steps: deprotection of the 2,3-O-isopropylidene group, furan ring opening, dehydration condensation of the OH groups, and elimination of water.

An efficient and convenient strategy has been successfully developed for the preparation of novel hydroxylated alkaloid derivatives (also called fused multicyclic iminosugars) from p-toluenesulfonylated sugars through a Pictet–Spengler-type mechanism. This method is highly stereoselective, does not require metal catalysts, and capable of conducting gram level reactions (with a 53% yield). Some of such iminosugars had an intermediate antiproliferative effect on HCT116 tumor cells.

Comprehensive Summary Different novel fused multicyclic iminosugars were synthesized from D‐ribose tosylate, aniline and vinyl ethyl ether by one‐pot three‐component stereoselective [4+2] reaction at different temperatures. The iminium‐ion is the key intermediate for the reaction. As a result, several complex fused iminosugars 3a were obtained by aza‐Diels‐Alder mechanism at 60 °C, while a series of aza‐ C ‐glycosides 5a were prepared by Mannich reaction at room temperature accompanied by another tetrahydroquinoline‐fused iminosugars 4a (tricyclic derivatives) through aza‐Diels‐Alder cycloaddition. This strategy will help to construct structurally diverse and bioactive iminosugar analogues.

A series of unexpected semi-saturated fused multicyclic iminosugars were synthesized by one-pot stereoselective three-components reactions of D-ribose tosylate, aniline and cycloketenes at heating condition. The N-aryl enamine derived from iminium-ion is the key intermediate for the reaction. As a result, several novel complex fused iminosugars 3a/4a were obtained through aza hetero Diels-Alder mechanism at 80 oC. This strategy will help to prepare the bioactive iminosugar analogues with structural diversity.

In this paper, a mild strategy for the oxidative cleavage of carbon-carbon bonds catalyzed by Lewis acid was developed in air condition at room temperature. Under such conditions, the bis-carbonyl compounds 3 were directly afforded from the reaction of D-ribose tosylate 1 and aniline in excellent yields through the oxidative cleavage of the key intermediate iminium-ion A and its tautomer enamine B. A series of N-arylated lactam-type iminosugars 5 were then successfully obtained by removing the isopropylidene group from 3 with the aid of the condensation agent DCC. Additionally, reduction of A and the removal of the isopropylidene group could provide N-arylated iminosugars 4. This strategy enables the oxidative cleavage of carbon-carbon bonds under mild conditions and facilitates the synthesis of the novel iminosugars with potent biological activity.

A simple and efficient one-pot synthetic protocol has been developed for the synthesis of 3-arylamino-2-polyhydroxyalkyl-substituted indoles by using unprotected sugars and aromatic amines. The protocol is simple to carry out with high yields under mild reaction conditions, and has atom economy with a good substrate scope and functional group tolerance, providing a new alternative route for the synthesis of structurally diverse indole derivatives. A simple and efficient one-pot synthetic protocol has been developed for the synthesis of structurally diverse indole derivatives by using unprotected sugars and aromatic amines.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An efficient and simple one-pot synthesis of structurally diverse novel tetrahydroquinoline-fused iminosugars was developed through the aza-Diels-Alder mechanism. The adaptability of this method has been demonstrated by a variety of imines and d/l-ribose tosylates, and both, electron-donating and -withdrawing substituted imines proceed well. In addition, this reaction is characterized by simple operation, good yield, and high atom economy. Some synthetic iminosugars showed moderate anti proliferation of HCT116 tumor cells.

An efficient and convenient strategy has been successfully developed for the preparation of novel furantetrahydroquinoline derivatives using d/l-ribose with a 2,3-O-isopropylidene group through the aza-Diels-Alder mechanism. This method has high atom and step economy, high stereoselectivity, and gram-scale synthesis (yield 67%).