Synthesis of C‐1 Alkyl and Aryl Glycals from Pyranosyl or Furanosyl Chlorides by Treatment with Organolithium Reagents

Abstract

Glycosyl chlorides, with ether or isopropylidene acetal protecting groups, readily available from furanoses or pyranoses, can be conveniently transformed into C‐1 alkyl or aryl glycals by reaction with alkyl or aryl organolithium reagents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Synthesis of furanoid and pyranoid C-1 aryl glycals by reaction of glycosyl chlorides with organolithium reagents

“…In agreement with our previous results, 16,18 we found they both led to the expected C-1 phenyl glycals in moderate yields (Scheme 3). We next turned our attention to the use of aryl organilithium reagents other than commercially available, PhLi.…”

“…Extractive work-up was followed by a quick flash chromatography (EtOAc/hexane 20%) to give C-1 glycal 16 (58 mg, 71% (18). A cooled (-78 ºC) solution of 1-methoxynaphtalene (293 µL, 2 mmol) in dry THF (1 mL) was treated with t-BuLi (1.17 mL, 1.7 M solution in pentane, 2 mmol) and the reaction mixture was allowed to warm to 0 ºC and then stirred for 2h.…”

“…6, with commercially available organolithium reagents, where the carbohydrates exerted as the electrophilic partner. 16,17 We have since evaluated the scope of the approach 18 and, in this paper, we describe the preparation of furanoid and pyranoid C-1 aryl glycals from the reaction of furanosyl and pyranosyl chlorides with aryllithium derivatives generated by directed ortho-metalation of aromatic derivatives, vide infra. Furthermore, the furanoid C-1 glycals prepared in this study can be easily transformed into homochiral 2,5-disubstituted furans.…”

Tetrasubstituted C‐Glycosylidenes and C‐Glycosyl Compounds from Di‐ and Monobromo‐Substituted exo‐Glycals

“…[23,24] In particular, Suzuki and Stille cross-coupling reactions have been successfully applied to 1Ј-halo-substituted exo-glycals obtained by halogenation of methylene-exo-glycals. [25] Various aryl, heteroaryl, vinyl or alkynyl groups have been introduced stereoselectively onto exo-glycal vinyl halide functionalities. [26] The one-step synthesis of exo-glycals developed in our group seemed attractive for further functionalization, offering access to more complex representatives of this interest-ing class of compounds ( Figure 1).…”

Iron(iii) chloride-catalyzed activation of glycosyl chlorides

“…Using this prior knowledge, we theorized that glycosyl chlorides may also offer a promising new substrate for the catalytic activation with FeCl 3 . To test this hypothesis, we chose known per-benzylated glucosyl chloride donor 1 23 to couple with the standard glycosyl acceptor 2. 48 The glycosylation was set-up in the presence of molecular sieves (4 Å) in dichloromethane.…”