Synthesis of hydroxylated pyrrolidines derivatives as potential inhibitors of SAH/MTA nucleosidase

Regulatory Mechanisms of the LuxS/AI-2 System and Bacterial Resistance

The quorum-sensing (QS) system is an intercellular cell-cell communication mechanism that controls the expression of genes involved in a variety of cellular processes and that plays critical roles in the adaption and survival of bacteria in their environment. The LuxS/AI-2 QS system, which uses AI-2 (autoinducer-2) as a signal molecule, has been identified in both Gram-negative and Gram-positive bacteria. As one of the important global regulatory networks in bacteria, it responds to fluctuations in the numbers of bacteria and regulates the expression of a number of genes, thus affecting cell behavior. We summarize here the known relationships between the LuxS/AI-2 system and drug resistance, discuss the inhibition of LuxS/AI-2 system as an approach to prevent bacterial resistance, and present new strategies for the treatment of drug-resistant pathogens.

Synthesis of mono- and di-hydroxylated prolines and 2-hydroxymethylpyrrolidines from non-carbohydrate precursors

Natural and synthetic imino sugars are biologically important as glycosidase inhibitors. This review includes selected syntheses of 3-hydroxyproline, 4-hydroxyproline, 3,4-dihydroxyproline, 2-hydroxymethyl-3-hydroxypyrrolidine and 2-hydroxymethyl-pyrrolidine-3,4-diol, which exhibit glycosidase inhibitory and various other biological activities.

First asymmetric hetero Diels-Alder reaction of 1-sulfinyl dienes with nitroso derivatives. A new entry to the synthesis of optically pure 1,4-imino-L-ribitol derivatives

Hetero Diels-Alder (HDA) cycloaddition of chiral 1-p-tolylsulfinyl-1,3-pentadiene with benzyl nitrosoformate, under mild conditions, yields 2H-1,2-oxazine 3 with complete regioselectivity and pi-facial diastereoselectivity. Sequential osmylation and protection of the resulting glycol gives the oxazine 5 which is directly transformed into enantiomerically pure 1,4,5-trideoxy-1,4-imino-L-ribitol 8 by reduction under Pd/C.

Synthesis of (2R,3R,4S)-2-hydroxymethylpyrrolidine-3,4-diol from (2S)-3,4-dehydroproline derivatives

(2R,3R,4S)-2-Hydroxymethylpyrrolidine-3,4-diol (1,4-dideoxy-1,4-imino-D-ribitol) was synthesized in five steps from N-protected (2S)-3,4-dehydroproline methyl esters. The stereoselective reaction of osmium tetraoxide with dehydroproline derivatives gave high yields of (2S,3R,4S)-3,4-dihydroxyprolines (2,3-trans-3,4-cis-3,4-dihydroxy-L-prolines) accompanied by small amounts (< 15%) of the diastereomeric (2S,3S,4R)-3,4-dihydroxyprolines (2,3-cis-3,4-cis-3,4-dihydroxy-L-prolines). The mixture of the diastereomeric glycols was converted into the isopropylidene acetals, and the isomers separated efficiently on a preparative scale. The resulting protected (2S,3R,4S)-3,4-dihydroxyproline methyl ester was reduced (LiBH4) to the 2-hydroxymethylpyrrolidine and deprotected, resulting in the production of (2R,3R,4S)-2-hydroxymethylpyrrolidine-3,4-diol in high yield and in high purity. The 1H and 13C NMR signals of the product have been unambiguously assigned using two-dimensional NMR techniques, and the identity of the title pyrrolidine confirmed by comparisons of its spectra with those reported for the authentic material.