Enhanced Diastereoselectivity in β-Mannopyranosylation through the Use of Sterically Minimal Propargyl Ether Protecting Groups
- 23 March 2006
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 71 (8) , 3064-3070
- https://doi.org/10.1021/jo0526789
Abstract
2-O-Propargyl ethers are shown to be advantageous in the 4,6-O-benzylidene acetal directed β-mannosylation reaction. The effect is most pronounced when the O3 protecting group is a bulky silyl ether or a glycosidic bond; however, even with a 3-O-benzyl ether, the use of a 2-O-propargyl ether results in a significant increase in diastereoselectivity. The beneficial effect of the propargyl ether is thought to be a combination of its minimal steric bulk, as determined by a measurement of the steric A-value and of its moderately disarming nature, as reflected in the pKa of propargyl alcohol. Conversely, the application of a 3-O-propargyl ether in the benzylidene acetal directed mannosylation has a detrimental effect on stereoselectivity, for which no explanation is at present available. Deprotection is achieved by base-catalyzed isomerization of the propargyl ether group to the corresponding allenyl ether, followed by oxidative cleavage with N-methylmorpholine N-oxide and catalytic osmium tetroxide.Keywords
This publication has 55 references indexed in Scilit:
- Stereoselective Glycosylation Reactions with Chiral AuxiliariesAngewandte Chemie International Edition in English, 2005
- Direct Chemical Synthesis of the β-d-Mannans: The β-(1→2) and β-(1→4) SeriesJournal of the American Chemical Society, 2004
- Benzylidene Acetal Fragmentation Route to 6-Deoxy Sugars: Direct Reductive Cleavage in the Presence of Ether Protecting Groups, Permitting the Efficient, Highly Stereocontrolled Synthesis of β-d-Rhamnosides from d-Mannosyl Glycosyl Donors. Total Synthesis of α-d-Gal-(1→3)-α-d-Rha-(1→3)- β-d-Rha-(1→4)-β-d-Glu-OMe, the Repeating Unit of the Antigenic Lipopolysaccharide from Escherichia hermannii ATCC 33650 and 33652Journal of the American Chemical Society, 2004
- Chemical Synthesis of Normal and Transformed PSA GlycopeptidesJournal of the American Chemical Society, 2003
- The 3,4-O-Carbonate Protecting Group as a β-Directing Group in Rhamnopyranosylation in Both Homogeneous and Heterogeneous Glycosylations As Compared to the Chameleon-like 2,3-O-CarbonatesThe Journal of Organic Chemistry, 2003
- Influence of the 4,6-O-Benzylidene, 4,6-O-Phenylboronate, and 4,6-O-Polystyrylboronate Protecting Groups on the Stereochemical Outcome of Thioglycoside-Based Glycosylations Mediated by 1-Benzenesulfinyl Piperidine/Triflic Anhydride and N-Iodosuccinimide/Trimethylsilyl TriflateThe Journal of Organic Chemistry, 2003
- Toward Fully Synthetic N‐Linked GlycoproteinsAngewandte Chemie International Edition in English, 2003
- Solid-Phase Synthesis of β-MannosidesJournal of the American Chemical Society, 2002
- Direct Synthesis of β-Mannans. A Hexameric [→3)-β-d-Man-(1→4)-β-d-Man-(1]3 Subunit of the Antigenic Polysaccharides from Leptospira biflexa and the Octameric (1→2)-Linked β-d-Mannan of the Candida albicans Phospholipomannan. X-ray Crystal Structure of a Protected TetramerJournal of the American Chemical Society, 2001
- A Paramagnetic Octahedral Rhodium(III) ComplexJournal of the American Chemical Society, 1965