Surface-Tethered Iterative Carbohydrate Synthesis: A Spacer Study
摘要:
Comparative study of Surface-Tethered Iterative Carbohydrate Synthesis (STICS) using HPLC-assisted experimental setup clearly demonstrates benefits of using longer spacer-anchoring systems. The use of mixed self-assembled monolayers helps provide the required space for glycosylation reaction around the immobilized glycosyl acceptor. Both extension of the spacer length and using mixed self-assembled monolayers help promote the reaction, and the beneficial effects may include moving the glycosyl acceptor further out into solution and providing additional conformational flexibility. It is possible that surface-immobilized glycosyl acceptors with a longer spacer (C8-O-C8)-lipoic acid have a higher tendency to mimic a solution-phase reaction environment than acceptors with shorter spacers.
Reductive cross-coupling of aryl halides with ubiquitous alkyl tosylates was developed using a combination of nickel and vitamin B12 catalysts. The tosylate was activated by reduced vitamin B12 to form alkyl cobalt(III) which served as a good alkylating agent for aryl-nickel species, leading to the C(sp3)–C(sp2) bond formation.