Abstract
A removable protecting group has been identified that allows the products of widely-used cross dehydrogenative couplings to be synthetically elaborated. The method can be used with enantiopure amines with no loss of enantiomeric excess. The methodology is exemplified by a new synthesis of enantiopure praziquantel, the drug used in the treatment of millions of people suffering from the neglected tropical disease, schistosomiasis.
Highlights
A removable protecting group has been identified that allows the products of widely-used cross dehydrogenative couplings to be synthetically elaborated
The methodology is exemplified by a new synthesis of enantiopure praziquantel, the drug used in the treatment of millions of people suffering from the neglected tropical disease, schistosomiasis
We show that using a para-methoxyphenyl (PMP) substituted amine (4, Scheme 1C) facilitates the desired Cross dehydrogenative coupling (CDC) reaction, after which deprotection allows for further elaboration of the unmasked amine; the conditions permit the synthesis of enantioenriched CDC products
Summary
A removable protecting group has been identified that allows the products of widely-used cross dehydrogenative couplings to be synthetically elaborated. Greater synthetic usefulness of CDC protocols would be demonstrated if the N-protecting group could be removed and the products elaborated. An obvious solution is to use a more labile protecting group such as a carbamate (e.g., Boc, Troc and Cbz, 3, Scheme 1B) but there are few such methodologies describing successful CDC reactions in the published literature.[2] We show that using a para-methoxyphenyl (PMP) substituted amine (4, Scheme 1C) facilitates the desired CDC reaction, after which deprotection allows for further elaboration of the unmasked amine; the conditions permit the synthesis of enantioenriched CDC products.
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