ChemInform Abstract: A Straightforward Approach Towards Substituted cis Hydroxyprolines.

Abstract

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Claisen Rearrangement over the Past Nine Decades

“…As discussed earlier, rearrangement of chelated allylic ester enolates in the presence of chiral ligands such as quinine afforded chiral γ,δ-unsaturated amino acids . This reaction was successfully applied to the preparation of cis -hydroxyprolines directly incorporated into peptides by a sequence consisting of iodolactonization, bicyclization, and nucleophilic lactone ring opening with amino acids and peptides (Scheme ) 163 …”

“…162 This reaction was successfully applied to the preparation of cis-hydroxyprolines directly incorporated into peptides by a sequence consisting of iodolactonization, bicyclization, and nucleophilic lactone ring opening with amino acids and peptides (Scheme 163). 186 A synthetic sequence involving an enantioselective aza-Claisen rearrangement was developed for the synthesis of optically active cis-3-arylproline deriva- tives, 187 interesting building blocks in the preparation of biologically active cyclopeptides. The synthesis of the starting materials was performed by Pd(0)catalyzed amination of the corresponding N-allyl mesylates with optically active proline derivatives acting as the chiral auxiliaries (Scheme 164).…”

Asymmetric Induction of the Iodolactonization Reaction of α-Sulfurated γ-Unsaturated Amides

“…When these compounds are substituted in the α position, a high 1,3-asymmetric induction is usually observed: trans selectivity with amides in contrast with cis selectivity with acids. Various substituents have been studied: alkyl, oxygenated, and halogenated functions, amino groups, and phosphonate . Surprisingly, the cyclization of sulfurated amides (with an unsubstituted double bond) has not been studied .…”