Described here is 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 the key iminium-ion/enamine intermediates by [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 by a variety of substituted anilines on which both electron-donating and electron-withdrawing were employed in the reactions well. Notably, the treatment of the fused multicyclic iminosugar 4 with TFA efficiently leads to an inter-esting unexpected pyridinium salt (8) possible via four steps in sequence: deprotection of 2,3-O-isopropylidene group, furan ring open-ing, intramolecular elimination of water, and dehydration condensation of OH groups.

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.

An efficient and simple one-pot synthesis of structurally diverse novel tetrahydroquinolin fused iminosugars was developed through the aza-Diels-Alder(Povarov mechanism) 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 are employed in reaction 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.