The 3,4-O-carbonate protecting group as a beta-directing group in rhamnopyranosylation in both homogeneous and heterogeneous glycosylations as compared to the chameleon-like 2,3-O-carbonates
Crich, D; Vinod, AU; Picione, J
| HERO ID | 5417774 |
|---|---|
| In Press | No |
| Year | 2003 |
| Title | The 3,4-O-carbonate protecting group as a beta-directing group in rhamnopyranosylation in both homogeneous and heterogeneous glycosylations as compared to the chameleon-like 2,3-O-carbonates |
| Authors | Crich, D; Vinod, AU; Picione, J |
| Journal | Journal of Organic Chemistry |
| Volume | 68 |
| Issue | 22 |
| Page Numbers | 8453-8458 |
| Abstract | It is demonstrated that the beta-selectivity observed in the insoluble silver salt mediated couplings of 2,3-O-carbonate-protected rhamnosyl bromides is uniquely due to the heterogeneous nature of the reaction. In homogeneous solution these same donors are alpha-selective, a fact that is attributed to the half-chair conformation of these substances which reduces the energy barrier to oxacarbenium ion formation. It is suggested that the 2,3-O-carbonate group be dubbed torsionally arming in the manno- and rhamnopyranose series. When the carbonate group is removed to the 3,4-O-position a beta-selective system is formed, in both homogeneous and heterogeneous conditions, and it is demonstrated that this selectivity arises from the combination of the electron-withdrawing nature of the carbonate and its inability to take part in neighboring participation. |
| Doi | 10.1021/jo035003j |
| Pmid | 14575470 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |