A mild method for the synthesis of anomerically allylated -glycopyranosides and -glycofuranosides

Stereocontrolled Access to Higher Sugars (Non-1-en-4-ulopyranosyl Derivatives) and Glycomimetics [3-(β-D-Glycopyranosyl)-1-propenes and(3Z)-4,8-Anhydro-nona-1,3-dienitols]

“…-gluco, [13,16] -manno, [16,17] -galacto, [16,18Ϫ20] lactose, [16,20,21] -ribo (BF 3 ·OEt 2 , TMSOTf, ZnBr 2 ), [22Ϫ24] and other [16,23Ϫ25] ], benzoyloxy, [23,24,26] 2,4,6-trimethylbenzoyloxy, [16] 4-nitrobenzoyloxy, [7,24] nitrate, [27] bromide, [13] chloride, [10,12] and fluoride. [28] 3-Glycosyl-1-propenes could also be prepared using allyltrimethylsilane by Lewis acid-catalyzed opening of anhydro sugars (1,2-, [9] 1,4-, [29] and 1,6-anhydro sugars [7] ) of radical-mediated allylation of 1؊3, [59,60] we found it preferable to resort to photolytic conditions, where the temperature of the reaction mixture was maintained below ca.…”

Total Synthesis of the Fungal Metabolite Trienylfuranol A through Nucleophilic Diastereodivergent Additions to Oxocarbenium Ions

“…We started the synthesis of the targeted cis-trisubstituted furan V from the O-acetyl substrate 9 by a homologation reaction with allyltrimethylsilane as C-nucleophile in the presence of Lewis acid. [16] We have used SnBr 4 as Lewis acid which is widely employed by Woerpel and co-workers for fivemembered-ring oxocarbenium ions [8a] and used recently by Ghosh and co-workers for the synthesis of amphirionin-4 [17] and monocerin, [18] while other Lewis acids such as BF 3 • OEt 2 , TiCl 4 or TMSOTf are described as less efficient. In our hands, with these conditions, the nucleophilic substitution of O-acetyl moiety of compound 9 with allyltrimethylsilane provided to the desired allylated compound 10 in good yield with an excellent αselective substitution as previously observed by Ghosh and coworkers (Scheme 3).…”

Synthesis of N,N,O-Trisubstituted Hydroxylamines by Stepwise Reduction and Substitution of O-Acyl N,N-Disubstituted Hydroxylamines

“…The scope of the hydroxylamine-forming process was further expanded by the replacement of triethylsilane in the final reduction by other suitable nucleophiles. Thus, adapting literature methods for C -glycoside formation − and for the reductive allylation of α-acetoxy ethers, , DIBAL-mediated reductive acetylation of 2a and 2b was followed by treatment of the intermediate O -(α-acetoxybenzyl)­hydroxylamines 5a and 5b with allyltributylstannane in the presence of BF 3 ·OEt 2 between −78 and 0 °C to give the trisubstituted hydroxylamines 7a and 7b in 82% and 54% isolated yields, respectively, for the two step protocol (Table , entries 1 and 2). The reductive allylation could also be conducted in high yield with the isolated and sterically hindered O -(α-acetoxyalkyl)­hydroxylamines 2g (Table , entry 3).…”