Intramolecular (4+3) Cycloadditions of Pyrroles and Application to the Synthesis of the Core of Class II Galbulimima Alkaloids.

The first intramolecular (4+3) cycloaddition of pyrroles with epoxy enolsilanes as the electrophiles was developed and used to generate optically-enriched cycloadducts containing the nortropane substructure in good yields. Using this pyrrole cycloaddition as the key step, we achieved the asymmetric synthesis of a nortropane compound bearing the BCDEF ring structure common to the Class II galbulimima alkaloids.

Synthesis of 3-acyloxyxanthone derivatives as α-glucosidase inhibitors: A further insight into the 3-substituents' effect.

Considerable interest has been attracted in xanthone and its derivatives because of their important biological activities. In this paper, a series of novel 3-arylacyloxyxanthone derivatives 2a-p were synthesized and evaluated for their biological activities toward α-glucosidase. In comparison to the parent 1,3-dihydroxylxanthone 1a, 3-arylacyloxy derivatives 2a-p with additional aromatic ester groups at 3-position show up to 13.

Toward potent α-glucosidase inhibitors based on xanthones: a closer look into the structure-activity correlations.

A series of novel xanthone derivatives 6-16 having non-coplanar and flexible structures were synthesized as potent α-glucosidase inhibitors. Biological evaluation indicated that compounds 6-12 bearing one or two naphthol moieties exhibited up to 30-fold enhanced activities compared with their corresponding parent compounds 2-5, whereas compounds 13-16 bearing one dihydroxylnaphthalenyl group showed decreased activities compared with their corresponding analogs 6-9 having one naphthol group. Among them, compounds 7-8, 10-12 and 15 were more active than 1-deoxynojirimycin, a well-known inhibitor for α-glucosidase.