Jiansong Sun

Current Synthesis of Triterpene Saponins

Triterpene saponins are a structurally and biologically diverse class of glycoconjugates of triterpenes that are widely distributed in terrestrial plants and some marine organisms. Current synthesis of these complex glycoconjugates has been discussed, whereupon the stereocontrolled glycosylation, global protection/deprotection, and the total synthesis of four unusual triterpene saponins are highlighted.

Efficient Synthesis of Lupane-Type Saponins via Gold(I)-Catalyzed Glycosylation with Glycosyl ortho-Alkynylbenzoates as Donors

Glycosylation of the acid labile betulin and betulinic acid derivatives was achieved with glycosyl ortho-hexynylbenzoates as donors under the catalysis of PPh(3)AuNTf(2); this enabled the efficient synthesis of lupane-type saponins, as exemplified by the total synthesis of the proposed betulinic acid trisaccharide from Bersama engleriana.

Synthetic access toward the diverse ginsenosides

All the possible types of the protopanaxatriol and protopanaxadiol glycosides, the major active yet extremely heterogeneous principles of ginsengs, could be accessed by the present sequence of transformations, including global removal of the sugar residues from the crude ginseng extracts and stepwise elaboration of the glycans onto the aglycone. In particular, intramolecular hydrogen-bonding and neutral conditions have enabled glycosylation of the highly sterically hindered and acid labile dammarane C20-OH.

Construction of interglycosidic N-O linkage via direct glycosylation of sugar oximes.

Direct glycosylation of sugar oximes and HONHFmoc has been realized for the first time by using glycosyl ortho-hexynylbenzoates as donors under the catalysis of PPh(3)AuOTf, providing an effective approach to the synthesis of N-O linked saccharides, which are of great biological interest.

Synthesis of Oligomeric 4-(Glycosyloxy)benzoate Macrocyclic Glycosides

Clemoarmanoside A and Clemahexapetoside A, two novel cyclic dimers of 4-(glycosyloxy)benzoates containing the unusual d-allopyranose as one of the sugar units, were synthesized for the first time. The convenient synthetic approach was adapted to the assembly of the symmetrical trimeric, tetrameric, and pentameric congeners. The synthesis clarified the discrepancy in the NMR data reported for the natural products. X-ray diffraction analysis of Clemahexapetoside A revealed that it adopted an armchair conformation with two carbohydrate rings as the arms and two aromatic rings as the back and seat, respectively.

CCDC 1400856: Experimental Crystal Structure Determination

Related Article: Renzeng Shen, Xin Cao, Stephane Laval, Jiansong Sun, Biao Yu|2016|J.Org.Chem.|81|10279|doi:10.1021/acs.joc.6b01265