An Efficient O-Monoalkylation of Dimethyl l-Tartrate via O-Stannylene Acetal with Alkyl Halides in the Presence of Cesium Fluoride

Abstract

Selective O-monoalkylation of the vic-glycol of dimethyl l-tartrate with alkyl halides has been found to take place smoothly under mild conditions in the presence of cesium fluoride.

Regioselective synthesis of long-chain ethers and their sulfates derived from methyl β-d-galactopyranoside and derivatives via dibutylstannylene acetal intermediates

“…It was found that the reactions of the long-chain alkyl bromides with dibutylstannylene acetals using the conditions of Danishefsky and Hungate 27 and by Nagashima and Ohno, 28,29 that is, in DMF with added cesium fluoride, gave somewhat better yields than the first conditions developed for alkylation reactions of dibutylstannylene acetals by Veyrières and co-workers, 22 that is, in benzene or toluene with added tetraalkyl ammonium halides (in Table 1, compare entry 2 with entry 4 or 8). Reactions of dibutylstannylene acetals with active alkyl halides, methyl iodide, benzyl iodide, and benzyl bromide occur in DMF with added cesium fluoride at rt; 29 the less active alkyl bromides used here react very slowly at room temperature (see entry 3).…”

Synthese von pentaantennären N‐Glycanen mit Bisecting‐GlcNAc und Core‐Fucose

“…Ausgehend von Benzylmannosid (2) wurde über ein Stannylenacetal eine 3-O-Allylierung (3) erreicht (Schema 2). [20,21] Die dreifache Glycosylierung (6 ¾quiv. Donor 1) führte zum Tetrasaccharid 4 (77 %), das zu 5 desallyliert wurde.…”

Convergent Synthesis, NMR and Conformational Analysis of Tetra- and Pentasaccharide Haptens of the Shigella flexneri Serotype 5a O-Specific Polysaccharide

“…This in turn was obtained from allyl α/β--rhamnopyranoside (16). [21] Regioselective introduction of a para-methoxybenzyl group at the equatorial hydroxyl of the corresponding dibutylstannylene acetal intermediate, by use of p-methoxybenzyl chloride in the presence of caesium fluoride, [22] gave the two monoprotected anomers 17 (6.9%) and 18 (66%), as ascertained by the NMR spectroscopic data. [19,20,23] Benzylation of 18 gave 19 (81%), which was de-O-allylated to yield the hemiacetal 20 (82%) by a twostep process involving iridium()-catalysed isomerisation [24] of the allyl glycoside to the prop-1-enyl glycoside and subsequent hydrolysis.…”

“…Indeed, although the use of a residue C precursor with a non-participating group at position 2 did result in the formation of the β-CD condensation product (22), the route to 24 compared favourably with that to 12 in terms of yield and number of steps. The complete 1 H assignments of the methyl glycosides 1 and 2, summarised in Table 1, were based on combined analysis of one-and two-dimensional 1 H NMR spectra including DQF-COSY [28] and TOCSY.…”