Vitamin B12 Catalysis of Zinc-Mediated 6-Deoxy-6-iodopyranoside Fragmentation: A Mild and Convenient Preparation of ω-Unsaturated Hexose Derivatives (5-Hexenoses)
The known zinc-mediated preparation of 5-hexenoses by fragmentation of 6-iodopyranosides can be performed in a simple, fast, and mild way, with less side reactions, when vitamin B12 is employed as a catalyst.
A Short Synthetic Route to the Calystegine Alkaloids
作者:Philip R. Skaanderup、Robert Madsen
DOI:10.1021/jo020645c
日期:2003.3.1
An efficient strategy is described for the synthesis of enantiopure calystegine alkaloids. The key step employs a zinc-mediated fragmentation of benzyl-protected methyl 6-iodo-glycosides followed by in situ formation of the benzyl imine and Barbier-type allylation with zinc, magnesium, or indium metal. Stereochemistry in the pivotal allylation is controlled by the choice of the metal. The functionalized
Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/<i>syn</i>-dihydroxylation
作者:Michał Malik、Sławomir Jarosz
DOI:10.3762/bjoc.12.255
日期:——
Synthesis of novel polyhydroxylated derivatives of decalin is described. The presented methodology consists in a one-pot copper-catalyzed 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse
A systematic study of diastereoselective nucleophilic addition of Grignard reagents to six-membered chiral tri-O-benzyl cyclicnitrones is described. With all eight chiral cyclicnitrones and asymmetric reaction conditions in hand, a practical methodology is established for the preparation of diverse 1-deoxyazapyranosides bearing various stereogenic centers.
Stereoselective SmI2-mediated conversion of carbohydrates into cyclopentanols
作者:J.J. CronjéGrové、Cedric W. Holzapfel、D.Bradley G. Williams
DOI:10.1016/0040-4039(95)02380-1
日期:1996.2
Carbohydrate derivatives were employed as precursors in the synthesis of stereodefined cyclopentanols. This rapid conversion was effected by a zinc-assisted Grob-fragmentation, followed by a stereocontrolled SmI2-mediated cyclisation.