N. Dieltiens

A straightforward ring transformation giving polymethylenebis(hydantoins) was extended, as these are HMBA analogues. Firstly, ethyl or allyl pyroglutamate was carbamoylated with a diisocyanate. Upon treatment with KOtBu in allyl alcohol the bis(carbamoyllactam) rearranged to give the hydantoin, which was followed by the ring-opening of the pyrrolidinone with formation of the allyl ester. These compounds were subsequently ring-closed in the presence of second-generation Grubbs' catalyst to form macrocycles containing the ester functionality in the ring. It was established by HSQC experiments with inverse detection that only the E isomers were formed in the cases of the 24- and 26-membered heterocycles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

When a mixture of a pyroglutamate and an isocyanate in THF is treated with NaH, a ring transformation occurs leading to functionalised hydantoins. The novel reaction involves a ring-closing ring-opening sequence providing a new and straightforward access to an interesting class of heterocyclic compounds. Furthermore, starting from pyroglutamates allows the synthesis of highly substituted hydantoins under very mild conditions. This ring transformation in combination with ring-closing metathesis is used in a four-step reaction sequence for the synthesis of multi-functionalised bicyclic hydantoin derivatives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A short and elegant synthetic pathway was developed for the synthesis of 1,3-dioxo-hexahydropyrido[1,2-c][1,3]diazepine carboxylates, a new 1,3-diazepan-2,4-dione containing bicyclic moiety, starting from pyroglutamate esters.