An efficient preparation of optically active α-furfuryl amide by kinetic resolution using the modified sharpless asymmetric epoxidation reagents

Methods for the synthesis of polyhydroxylated piperidines by diastereoselective dihydroxylation: Exploitation in the two-directional synthesis of aza-C-linked disaccharide derivatives

“…Methods for the diastereoselective functionalisation of piperidines were developed using a racemic model ring system. Oxidative ring expansion[ 38 ] of the 2-furyl sulfonamide 11 , prepared by addition of n -butyl lithium to the N -tosyl imine of 2-furaldehyde,[ 39 ] was followed by protection to yield the piperidin-3-one 12 (Scheme 3 ). The N,O acetal was substituted,[ 40 ] both by reduction (→ 13 ) and by allylation (→ 14 ); the allylation reaction was highly diastereoselective (>95:<5 syn : anti ), presumably as a result of a strong stereoelectronic preference for pseudo -axial attack on the intermediate iminium ion (with a pseudo axial[ 40 ] butyl substituent) (Figure 1 ).…”

Chirally templated boronic acid Mannich reaction in the synthesis of optically active α-amino acids

“…Oxidative modification of furan rings to carboxy groups is well known in the literature and reports by Zhou et al had shown that oxidation of the furan ring in similar compounds to ours could be best achieved by ozonolysis. 14 However, in our hands, such a procedure gave only complex reaction mixtures and the ruthenium dioxide oxidation procedure, developed by Sharpless, was used instead. 16 Treatment of the sulfonamides 10a-e with ruthenium dioxide, using sodium periodate as the co-oxidant in a 2 : 2 : 3 mixture of water, carbon tetrachloride and acetonitrile, gave the N-tosylated amino acids 11a-e accompanied by lesser amounts (~7%) of the formamides 12a-e (Scheme 6).…”

Synthesis and biological evaluation of aspergillide analogue as anticancer agents

“…The pyranonelactol3 obtained in the above step was activated to the corresponding acetate by using acetic anhydride in presence of pyridine to give acetate 6.The activated pyranone acetate 6 obtained was subjected to Ferrier-type alkynylation with silylated alkyne14 in the presence of 30 mol% of strong Lewis Acid SnCl 4 to give alkyne adduct 7 in 82% yield.Theenone7 obtained was reduced chemoselectively to the allyl alcohol 8 under standard Luche conditions [21,22] ..The free hydroxy moiety of allyl alcohol 8 obtained was subjected to O-TBS protection in the presence of TBSOTf and lutidine as a base to give the corresponding TBS ether 9.The di-ester 9 obtained was subjected to ester hydrolysis with NaOH to produce acid alcohol 10.Acid functionality in 10 was activated with 2 4 6-trichloro benzoylchloride, TEA to its mixed anhydride, and then this mixed anhydride was slowly added with syringe pump to refluxing toluene and DMAP to generate the macrolide 1.…”