Supramolecular Architecture through Self-Organization of Janus-Faced Homoazanucleosides

An expeditious synthesis of novel DNA nucleobase mimics of (+)-anisomycin

A glycal based expeditious synthesis of novel nucleoside analogues of (+)-anisomycin is reported. Readily available tri-O-benzyl-D-glucal was converted to a partially protected trihydroxypyrrolidine that is used as a common scaffold for the introduction of various nucleobases at the primary hydroxyl centre. Nucleoside analogues possessing all four DNA bases have been synthesized. Selective acetylation at C3 position was carried out with two of these unnatural nucleosides in order to mimic the structure of (+)-anisomycin. Cytotoxicity studies of some of these nucleosides showed that they display weaker activity on HeLa cells than Ara-C.

Double-headed nucleic acids condense the molecular information of DNA to half the number of nucleotides

Nucleotide monomers that hold two nucleobases each, i.e. double-headed nucleotides, have been shown to form two sets of functional Watson-Crick base pairs when incorporated into dsDNA, and they hereby behave as dinucleotides. To form the basis for fully modified double-headed nucleic acids (DhNA), we have prepared three new DhNA monomers and can now demonstrate that the molecular information of 10 Watson-Crick base pairs can be condensed to highly stable 5-mer DhNA duplexes.

From Glycals to Nitrogen Heterocycles and Carbocycles via "Cleavage-Intramolecular Recombination Strategy"

Glycals (carbohydrate enol-ethers) have enjoyed profound applications in organic synthesis for more than a century. They not only serve as versatile glycosyl donors or as substrates for Ferrier rearrangement, but also find extensive synthetic applications especially as a "chiral pool" for accomplishing the synthesis of a variety of natural and biologically important compounds. As cyclic enol ethers, they demonstrate high reactivity and are among the most and variously transformable monosaccharide derivatives. The uniqueness of the reactivity of glycals is that they can be synthetically tuned to get a library of derivatives through stereo- and regioselective introduction of a variety of functional groups at C1, C2, C3 as well as C4 carbons of the sugar. We have developed a practical approach for stereoselective mono- and diamination of glycals and over the years utilized these scaffolds for the synthesis of a variety of biologically important nitrogen heterocycles and carbocycles through a "Diversity Oriented Approach". Our synthetic strategy in this direction mainly relied on the cleavage of ring O-C bond of the sugar followed by an "intramolecular recombination" reaction. Utilizing this strategy, we have accomplished the synthesis of several biologically important natural products, their analogues and related unnatural derivatives. Examples of such compounds reported from our group include polyhydroxypyrrolidines, DMDP, anisomycin, steviamine, pochonicine, conduramines, bulgecinine, aminocyclitols, azepanes, 4-hydroxy-D-proline, azanucleosides and their analogues. A personal account highlighting these syntheses is presented here.