Synthesis of C-arabinofuranosyl compounds. Phosphonate and carboxylate isosteres of d-arabinose 1,5-bisphosphate

Synthesis of Phosphonomethyl Tetrahydrofurans via the Mori-Tamaru Reaction of Phosphonodienes

Nickel-catalyzed reductive addition of phosphonodienes to aldehydes (the Mori-Tamaru reaction) gives hydroxy vinyl phosphonates in good yields with excellent control of the relative stereochemistry. Base-induced cyclization of the vinyl phosphonates yields phosphonomethyl-substituted tetrahydrofurans. Inversion of the hydroxyl stereochemistry by Mitsunobu reaction and then cyclization yields a different set of phosphonomethyl-substituted tetrahydrofuran diastereoisomers.

Total synthesis and stereochemical revision of acortatarins A and B

A first total synthesis of acortatarins A, B, and an enantiomer of the proposed structure of acortatarin B is described by using readily available d-sugars. This convergent total synthesis revealed the revision of the absolute configuration of acortatarin A and structural revision of acortatarin B. The key steps involved are regioselective epoxide opening with deprotonated 2,5-disubstituted pyrrole and spiroketalization.

D-Arabinose-based synthesis of homo-C-d4T and homo-C-thymidine

2,3,5-Tri-O-benzyl-D-arabinofuranosyl halides (chloride, bromide) were reacted with AllMgBr, MeMgBr, and VinMgBr to furnish anomeric mixtures of the C-glycosyl products. The factors that influenced the beta/alpha ratio are discussed. The alpha,beta-C-vinyl derivative was transformed into 1-deoxy-1-C-hydroxymethyl-beta- and -alpha-D-arabinofuranoses (2,5-anhydro-D-glucitol and -mannitol, respectively), separable after isopropylidenation step. 2,5-Anhydro-1,3-O-isopropylidene-D-glucitol was converted into 2,5-anhydro-6-O-triphenylmethyl-D-erythro-hex-3,4-enitol and 2,5-anhydro-4,6-di-O-benzoyl-3-deoxy-D-ribo-hexitol, which were coupled with N-3-benzoylthymine under the Mitsunobu conditions to furnish two analogs of nucleosides with a -CH(2)- insert between sugar moieties and thymine.

An efficient route for the synthesis of glycosyl phosphinic acids

An efficient method for the synthesis of glycosyl phosphinic acids (21) from the corresponding C-phosphonates is described. The route developed involves three steps: reduction of the glycosyl C-phosphonate to a primary phosphine, reaction of this product with an alkylating agent to afford a secondary phosphine, and finally oxidation to the phosphinic acid. Deprotection provides compounds suitable for testing as glycosyl phosphate analogues. Although the focus of this report is the synthesis of analogues of arabinofuranosyl-containing phosphate esters, the method should be readily applicable to other systems, carbohydrate or otherwise.

Synthesis of some biologically relevant beta-C-glycoconjugates

[reaction: see text] An esterification-RCM approach to a variety of biologically relevant beta-C-glycoconjugates is reported herein. A range of carboxylic acids were coupled with several different olefin alcohols 1 to provide esters 3. The esters were then converted to the final ring-closed product 6 in three steps in 49-60% overall yield. The formed compounds are biologically relevant and serve as stable carbohydrate mimics of the corresponding O-glycosides.

Synthesis and antituberculosis activity of C-phosphonate analogues of decaprenolphosphoarabinose, a key intermediate in the biosynthesis of mycobacterial arabinogalactan and lipoarabinomannan

The cell wall complex in mycobacteria, including the human pathogen Mycobacterium tuberculosis, is comprised in large part of two polysaccharides that contain a significant number of arabinofuranose residues. Both polysaccharides are assembled by a family of arabinosyltransferases that use decaprenolphosphoarabinose (3) as the donor species. In this paper, we describe the synthesis of a panel of C-phosphonate analogues of 3, which were designed to inhibit these arabinosyltransferases and thus block the biosynthesis of mycobacterial cell wall polysaccharides. A number of routes were explored for the preparation of the targets. The successful approach involved the synthesis of a protected C-phosphonate allyl ester 16, which was then coupled to an alkene via an olefin cross metathesis reaction. Subsequent reduction of the alkene with diimide and deprotection afforded the targets. Screening of these compounds in vitro against Mycobacterium tuberculosis revealed that one of the compounds, 15f, possessed antituberculosis activity, with an MIC value of 3.13 microg/mL.

Synthesis and biological activities of (4,6-di-O-phosphonato-beta-D-mannopyranosyl)-methylphosphonate as an analogue of 1L-myo-inositol 1,4,5-trisphosphate

The synthesis of the alpha and beta anomers of the title compound (1) was accomplished from D-mannose. In the key step, the phosphonate analogues of the mannopyranosyl phosphates were prepared by a direct Wadsworth-Emmons condensation of a protected mannose derivative (8) with tetraethyl methylenebisphosphonate under two-phase conditions. In vitro bioassays have shown that the beta anomer (1a) is a potent inhibitor of Ins(1,4,5)P3 3-kinase and inhibits other enzymes.