- Synthesis of 2-C- and 3-C-aryl pyranosides
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Lithium diphenylcuprate treatment of methyl 2,3-anhydro-4,6-O-benzylidene-D-pyranosides in which the anomeric substituent and the three-membered rings are cis oriented furnished the expected trans-diaxial opening products. When the relationship between the anomeric group and the epoxide was trans, the same experimental conditions led only to recovered starting material. Cyano cuprates of the type R2CuCNLi2 added stereoselectively to carbohydrate ketones at C-2 and C-3 from the opposite side relative to the anomeric substituent.
- Hladezuk,Olesker,Cleophax,Lukacs
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- Regiocontrolled Opening of Cyclic Ethers Using Dimethylboron Bromide
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The cleavage of various cyclic ethers (3- to 7-membered rings) was achieved under very mild conditions using dimethylboron bromide to afford the corresponding bromo alcohols.In particular, 2-substituted tetrahydrofurans were regioselectively cleaved by a predominantly SN2 - type mechanism favoring the formation of primary vs. secondary bromides.Dimethylboron bromide also cleaved chemoselectively substituted tetrahydrofurans in the presence of functional groups such as acyclic ethers, silyl ethers, esters, amides, ketones,etc.
- Guindon, Yvan,Therien, Michel,Girard, Yves,Yoakim, Christiane
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p. 1680 - 1686
(2007/10/02)
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- A CONVENIENT METHOD FOR THE PREPARATION OF 4,6-O-BENZYLIDENEGLYCALS FROM METHYL 2,3-ANHYDRO-4,6-O-BENZYLIDENE-α-D-HEXAPYRANOSIDES
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The reaction of methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (1) with ethylmagnesium bromide in the presence of CuI afforded 4,6-O-benzylidene-1,2-dideoxy-D-ribo-hex-1-enopyranoside (2).Similarly, methyl 2,3-anhydro-4,6-O-benzylidene-α-D-gulopy
- Tsuda, Nobuo,Yokota, Sumio,Kudo, Takashi,Mitsunobu, Oyo
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p. 289 - 292
(2007/10/02)
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