The metathesis reaction for side chain construction in carbocyclic sinefungin analogue synthesis

The naturally occurring nucleoside sinefungin has found considerable use in biological investigations. More extensive sinefungin studies have been limited because few analogues have been reported due to the synthetic challenges associated with such studies. Reported herein are preparative ways to two carbocyclic sinefungin analogues: 6′-deaminocarbocyclic sinefungin and (S)-6′-hydroxy-6′-deaminocarbocyclic sinefungin. The synthetic routes were made efficient and practical by the application of two metathesis reactions employing second generation Grubbs catalyst.     

Structure determination of a sildenafil analogue contained in commercial herb drinks

It was found from HPLC analysis that a commercial herb drink contains a putative sildenafil analog. In order to identify the sildenafil-like compound, separation and purification were carried out. The structure determination was performed based on routine 1D and 2D NMR experiments. Unlike sildenafil, the compound contains an ethylpiperazine instead of a methylpiperazine group. In addition, the piperazine and phenyl groups are connected through an acetyl group instead of the sulfonyl group of sildenafil.     

Solid-phase synthesis of carbocyclic nucleosides

[formula: see text] An efficient solid-phase synthesis of carbocyclic nucleosides has been developed. The key step is the palladium-catalyzed coupling of a purine derivative to a resin-bound allylic benzoate. The resulting products may be further functionalized on the solid phase. Acidic cleavage affords carbocyclic nucleosides, a class of compounds with demonstrated biological activity and substantial current interest.     

Synthesis of a novel conformationally locked carbocyclic nucleoside ring system

[reaction: see text] A fast and efficient synthetic route to novel Northern locked carbocyclic nucleosides (as precursors of carbocyclic locked nucleic acids or cLNAs) is described. The target nucleoside with a oxabicyclo[2.2.1]heptane ring system was prepared from a simple starting material, diethyl malonate. Ring closure by intramolecular O-alkylation provided the target ring system as the major isomer over the [3.2.0] oxetane system. The adenine moiety was introduced through a reactive triflate after inversion of the stereochemistry of the corresponding alcohol by oxidation and reduction.     

Access to [6.4.0]carbocyclic systems by tandem metathesis of dienynes. A step toward the synthesis of a PreD3-D3 transition state analogue

[reaction: see text] A new approach to the synthesis of linearly fused 6-8-6 tricarbocyclic systems, tandem ring-closing metathesis of dienynes, allows access to compounds with a carbon framework analogous to the proposed transition state of the isomerization of previtamin D(3) to vitamin D(3).