No abstract

The conversion of (±)‐hydratropaoyl chloride into (S)‐(+)‐hydratropic acid (4) can be achieved with (S)‐(−)‐1‐phenylethanol (2) as chiral auxiliary agent in the following way: Generation of the ketene (1) from the acid chloride in situ, reaction with (S)‐(−)‐(2) in the presence of a base to give a mixture of the diastereomers (3) [with pyridine, e.g., (S,S) :(R,S) = 88 :12], hydrolysis of (S)‐(+)‐(4) with recovery of (S)‐(−)‐(2).

Nach 30 min bei Raumtemperatur entsteht aus (3a) der N-deblockierte y-N-Glycosyl-asparagin-benzylester (4) kristallin rnit 67% Ausbeute. Unter den Bedingungen wird der primare Ester an C-6 des Glucosamins nicht angegriffen.Gegeniiber dem hlufig verwendeten Benzyloxycarbonyl(Z)-Rest bietet die Peoc-Schutzgruppe bei den Glycosyl-Peptiden drei Vorteile: