Regio- and Chemoselective Deprotection of Primary Acetates by Zirconium Hydrides
摘要:
A combination of DIBAL-H and Cp2ZrCl2 is shown to promote the regioselective cleavage of primary acetates on a broad scope of substrates, ranging from carbohydrates to terpene derivatives, with a high tolerance toward protecting groups and numerous functionalities found in natural products and bioactive compounds. Apart from providing highly valuable building blocks in only two steps from biosourced raw materials, this selective de-O-acetylation should also be strongly helpful to solve selectivity issues in organic synthesis.
3- and 4-Uloses Derived from N-Acetyl-D-glucosamine: A Unique Pair of Complementary Organocatalysts for Asymmetric Epoxidation of Alkenes
作者:Christof Schöberl、Volker Jäger
DOI:10.1002/adsc.201100735
日期:2012.3.16
The 4‐ulose and the 3‐ulose, both derived in two steps from the α‐methyl glycoside of N‐acetyl‐D‐glucosamine (GlcNAc), act as organocatalysts in the asymmetricepoxidation of alkenes, with unprecedented complementary enantioselectivity. The best results are found with α,β‐unsaturated esters as substrates, with enantiomeric ratios up to 90:10 and 11:89, respectively.