Synthesis of glycosides of 3-deoxy-4-thiopentopyranosid-2-uloses and their reduction products: 3-deoxy-4-thiopentopyranosides
作者:Marı́a Laura Uhrig、Oscar Varela
DOI:10.1016/s0008-6215(02)00292-6
日期:2002.11
Michaeladdition of common thiols to the enone system of (2S)-2-benzyloxy-2H-pyran-3(6H)-one (1) afforded the corresponding 3-deoxy-4-thiopentopyranosid-2-ulose derivatives (2-4). The reaction was highly diastereoselective, and the addition was governed by the quasiaxially disposed 2-benzyloxy substituent of the starting pyranone. As expected from the enantiomeric excess of 1 (ee > 86%) the corresponding
Enantiospecific Synthesis of Both Enantiomers of 2-Benzyloxydihydropyran-3-ones from Arabinose
作者:Oscar Varela、María Laura Uhrig
DOI:10.1055/s-2005-861833
日期:——
Approaches to the enantioselective synthesis of the useful building blocks (2R)- and (2S)-2-benzyloxy-2(H)-pyran-3(6H)-one (12 and 17, respectively) are described. The most direct and highly yielding route for the synthesis of 12 was based on the ‘one-pot’ preparation of benzyl 2-O-acetyl-arabinopyranoside 3,4-thionocarbonates (7 and 14) from benzyl β-l- or β-d-arabinopyranosides (1 and 13). Trimethylphosphite-promoted olefination, followed by O-deacetylation and oxidation gave the optically pure enantiomeric enones 12 and 17 in about 50% overall yield.
Stereocontrolled Diels−Alder Cycloadditions of Sugar-Derived Dihydropyranones with Dienes
作者:Christian A. Iriarte Capaccio、Oscar Varela
DOI:10.1021/jo020309w
日期:2002.11.1
dihydropyranone. The influence of other catalysts (BF(3) or iodine) employed for the glycosylation on the optical purity of the dihydropyranone was studied. Enantiomericallypure dihydropyranones 8b and 9c were obtained using chiral alcohols ((R)- and (S)-2-octanol, respectively) as glycosylating agents. Compounds 8a,b and 9a,c proved to be reactive dienophiles in thermal and Lewis acid-promoted Diels-Alder
Synthesis of enantiomerically pure enones (2-benzyloxypyran-3-ones) derived from pentoses
作者:Lucas Dada、Verónica E. Manzano、Oscar Varela
DOI:10.1016/j.carres.2019.05.005
日期:2019.6
enantiomerically pure enones were synthesized via an improved straightforward and high yielding sequence (70% overall) from benzyl pentopyranosides. However, the yields of both, the glycosylation of glycals as well as some specific reactions of the sequence from glycosides, were lowered when a p-nitro substituent was introduced into the benzyl group. These routes became impractical in the case of p-acetamidobenzyl
Synthesis of Optically Active 2-Alkoxy-2<i>H</i>-pyran-3(6<i>H</i>)-ones. Their Use as Dienophiles in Diels−Alder Cycloadditions
作者:Christian A. Iriarte Capaccio、Oscar Varela
DOI:10.1021/jo0106896
日期:2001.12.1
cycloadducts 9a-c and 10a were respectively obtained with good diastereofacial selectivity (>80%). Optimized Lewis acid promoted cycloadditions led to 9a-d and 10a,c in higher yields (approximately 80%) and with higher diastereoselectivities (>94%). The major products were formed by approach of the dienes from the less hindered face of the dihydropyranones, and the minor products (such as 11a) were formed