158991-97-0Relevant academic research and scientific papers
Fluorination of 2-hydroxy-hexopyranosides by DAST: Towards formyl C-glycofuranosides from equatorial-2-OH methyl hexopyranosides
Vera-Ayoso, Yolanda,Borrachero, Pastora,Cabrera-Escribano, Francisca,Carmona, Ana T.,Gomez-Guillen, Manuel
, p. 429 - 444 (2004)
Reaction of diversely configured and substituted, unbranched methyl D-hexopyranosides with the DAST in dichloromethane or acetonitrile led to normal substitution products and/or rearranged fluoro compounds (ring-contracted 2,5-anhydro-1-fluoro-1-O-methylhexitol derivatives, 2-methoxy-D-hexopyranosyl fluorides, and, for some 3-azido substrates, rearranged 2-azido-3-fluoro-D-hexopyranosides). When the reaction was performed in acetonitrile, the solvent participation as a nucleophile (Ritter reaction) was observed in one case. For a 2,4-unprotected 3-azido substrate, 2,3-dehydration and fluorination at C(4), the latter with epimerization, took place. 19F/1H and 19F/13C coupling constant values were systematically applied to discriminate between isomeric structures for fluorinated products, and for some, previously described, coming from five 3-branched-chain D- or L-hexopyranosides, thus discarding the previously reported structural assignment. From the synthetic point of view, the most outstanding result was the preparation of 2,5-anhydro-1-fluoro-1-O- methylhexitols, showing a latent formyl group functionality, a transformation, which was achieved in one case. A rationalization for the formation of the different types of product is also proposed.
REGIOSELECTIVE FORMATION OF DI-O-BENZYL-SUBSTITUTED HEXOPYRANOSIDES VIA STANNYLENE ACETAL INTERMEDIATES
Qin, Huiping,Grindley, T. Bruce
, p. 475 - 490 (2007/10/02)
The reactions of dibutylstannylene acetals derived from several methyl hexopyranosides with benzyl bromide have been investigated.These reactions occur readily in benzyl bromide at 85 deg C.At reaction times of one to two days, the major products are di-O-benzyl derivatives.In several cases, single di-O-benzyl derivatives are the predominant products: methyl α-D-glucopyranoside and methyl β-D-galactopyranoside gave the 2,6- and 3,6-di-O-benzyl ethers in 82 and 70percent yields, respectively.The species present in these reactions and the reaction pathway are discussed.
