A new ferrier system: 2-C-acetoxymethylglycals. A covenient entry to 2-C-methylene glycosides
01 Jan 1993-Journal of The Chemical Society, Chemical Communications (The Royal Society of Chemistry)-Iss: 18, pp 1394-1395
TL;DR: In this paper, the synthesis of tri-O-benzyl-2-C-acetoxymethyl glycals and subsequent Ferrier rearangement to give 2C-methylene glycosides is described.
Abstract: Syntheis of tri-O-benzyl-2-C-acetoxymethylglycals and subsequent Ferrier rearangement to give 2-C-methylene glycosides is described.
Citations
More filters
TL;DR: Various elimination procedures conducted on appropriate pyranoid and furanoid carbohydrate derivatives, especially on O-protected glycosyl halides afford cyclic vinyl ethers which Fischer (inappropriately) named glycals, form the major part of this chapter.
Abstract: Various elimination procedures conducted on appropriate pyranoid and furanoid carbohydrate derivatives, especially on O-protected glycosyl halides afford cyclic vinyl ethers which Fischer (inappropriately) named glycals. These are used extensively in general organic synthesis and for the preparation of non-carbohydrate natural products as well as biologically important complex carbohydrates and glycoconjugates. The best known member, tri-O-acetyl-D-glucal, is normally made from tetra-O-acetyl-alpha-D-glucopyranosyl bromide, is commercially available, and is used very frequently in this chapter to represent the family in examples of the reactions under discussion.
Because of the pronounced region- and stereoselectivities with which their addition reactions can be conducted, glycal derivatives are of major importance in synthesis. They also, however, take part in rearrangement processes that, likewise, have proved useful for synthesis. The principal one involves nucleophilic substitution of the allylic group with allylic rearrangement and results in products having double bonds in the 2, 3 positions and new substituents at the anomeric centers. By far the simplest and most commonly used way to this conversion involves the removal of the allylic substituent of the glycal and the generation of highly resonance-stabilized oxocarbenium ion intermediate. This may then react with nucleophiles at the anomeric center to give products as mixtures of diastereomers. Many examples and variations of this theme are described and form the major part of this chapter, but other ways are also considered
Almost no formal mechanistic studies have been carried out on the reactions in this chapter. Categorization of mechanism required for the treatment of this topic has been done on the basis of conditions used, product identification and largely, chemical intuition.
Keywords:
glycals;
transformation;
oxocarbenium ions;
regioselectivity;
diasterioselectivity;
nucleophilic substitutions;
homoallylic center;
addition-elimination reactions;
palladium;
leaving groups;
electrocyclic reactions;
unsaturated compounds;
free sugars;
glycosyl peroxides;
glycosyl caroxylates;
S-glycosides;
glycosyl halides;
glycosyl azides;
glycosyl phosphonates;
glycosyl hydrides;
furanoid glycols;
intramolecular applications;
reverse reaction;
reaction variations;
scope;
limitations;
configuration;
experimental procedures;
other methods
36 citations
TL;DR: In this article, a new catalyst system comprising AuCl3 and phenylacetylene was developed to promote the Ferrier rearrangement of glycals and 2-acetoxymethyl glycals with different nucleophiles, and also the O-glycosylation of 1-O-acetyl sugars.
34 citations
TL;DR: In this article, C-2 Methylene glycosides were synthesized from propargyloxymethyl glycals in a stereoselective manner using a catalytic quantity of AuCl3.
32 citations
TL;DR: In this paper, 2-C -acetoxymethyl glycal derivatives react with aliphatic alcohols in the presence of InCl 3 to furnish the corresponding 2-c -methylene glycosides in excellent yields and with exclusive α-selectivity.
24 citations
TL;DR: Recent developments in the synthesis and applications of 2-C-formyl-glycals, the versatile chiral intermediates, are summarized in this review.
22 citations
References
More filters
TL;DR: DMDC as well as 2'-deoxy-2'-methylidene-5-fluorocytidine (19a) showed potent antileukemic activity against murine L 1210 cells in culture and in vivo antitumor activity of DMDC against L1210 was also described.
Abstract: A new type of antineoplastic nucleoside, 2'-deoxy-2'-methylidenecytidine (DMDC) has been synthesized from the corresponding 2'-keto pyrimidine nucleosides 3 and 8 by the Wittig reaction. During the course of the reaction, we found that an intermediate betaine could pick a proton from the excess triphenylphosphonium bromide to form the 2'-phosphonium salts 5 and 10, which could be further converted into the 2'-deoxy-2'-methylidene nucleosides 4 and 9 by treatment with sodium hydride. Various 5-substituted DMDC derivatives 19a-e,h and their uracil congeners 16a-h were also synthesized from the corresponding 5-substituted uridines 12a-f,h. Among them, DMDC as well as 2'-deoxy-2'-methylidene-5-fluorocytidine (19a) showed potent antileukemic activity against murine L1210 cells in culture. The activity of DMDC and 19a toward various human tumor cells in culture compared with 1-beta-D-arabinofuranosylcytosine and 5-fluorouracil was also examined. In vivo antitumor activity of DMDC against L1210 was also described.
88 citations
TL;DR: In this article, Stannic chloride-catalysis was used for rearrangement of 3,4,6-tri-O -acetyl-1,5-anhydro-2-deoxy-d -hex-l-enitol.
77 citations
TL;DR: In this paper, the mechanisms of these reactions are discussed and a high degree of stereospecificity is obtained for dimeric 1,2-cis-2,deoxy-2-nitroso-α-D-aldopyranosyl chlorides.
Abstract: Reaction of nitrosyl chloride with acetylated glycals affords, with a high degree of stereospecificity, dimeric acetylated 1,2-cis-2-deoxy-2-nitroso-α-D-aldopyranosyl chlorides. Reaction of acetylated glycals with dinitrogen tetroxide, depending on the reaction conditions, can give either acetylated 2-deoxy-2-nitroso-α-D-aldopyranosyl nitrates as dimers or acetylated 2-nitroglycals. The mechanisms of these reactions are discussed.
53 citations
TL;DR: A short and straightforward route has been accomplished for the synthesis of C-2-formyl glycals by a Vilsmeier-Haack reaction of glycals.
52 citations
50 citations