Synthesis of Enantiopure .alpha.,.omega.-Diamino Dicarboxylates and Azabicycloalkane Amino Acids by Claisen Condensation of .alpha.-[N-(Phenylfluorenyl)amino] Dicarboxylates

Design, synthesis, and application of azabicyclo[X.Y.0]alkanone amino acids as constrained dipeptide surrogates and peptide mimics

“…Since the synthesis of the parent indolizidinone system was reviewed in 1997 (Scheme ),1 six methods have been reported for preparing this azabicycloalkane amino acid. The original syntheses involved formation of linear keto diaminoazelates 37 by Claisen condensation,21, 22 or Schöllkopf alkylation20 followed by reductive amination and lactam cyclization to form respectively N ‐(Boc)‐ and N ‐(Cbz)‐protected bicycles 38 and 39 .…”

Design, synthesis, and conformational analysis of azacycloalkane amino acids as conformationally constrained probes for mimicry of peptide secondary structures

“…Our strategy for synthesizing azabicyclo[X.Y.0]alkane amino acid tries to address the criteria raised above by joining together the ω‐carboxylates of two α‐aminodicarboxylates to provide a linear ketone intermediate (Scheme ) 29–36. Side chains may then be introduced by conjugate additions and alkylations of the ketone.…”

“…Our initial synthesis of indolizidin‐2‐one amino acid 7 illustrated the effective use of the PhF group for protection of glutamic acid in the stereoselective construction of azabicyclo[X.Y.0]alkane amino acid 29–31,§. A Claisen condensation between the ω‐methyl esters of L ‐ N ‐(PhF)glutamate diesters 3 was achieved using sodium bis(trimethylsilyl)amide as base in tetrahydrofuran (THF) to provide β‐keto ester 4 that was hydrolyzed and decarboxylated to give C2‐symmetric δ‐keto α,ω‐diaminoazelate 5 .…”

“…The interested reader should see Ref. 25 for a lead article as well as Reference 29 in Ref. 23 for reviews.…”

[3,3]-Acyloxy Rearrangement-Triggered Regioselective Hydration of δ-Acetoxy-α,β-Alkynoates/Halo Alkynes

“…While most of these studies have mainly focused on the hydration of terminal alkynes, studies to employ unsymmetrical internal alkynes for forming synthons of chemically distinctly reactive functionalities are limited. For instance, the Au-catalyzed regioselective hydration of alkynoates, complementary to classical base-mediated and Ti-Claisen condensations, provides a reliable method for generating β-keto esters, which is still underdeveloped. Hammond’s report (only applied for one substrate) on Au­(III)-catalyzed hydration is the only example except our recent study on neighboring acyloxy-assisted hydration for a broad-scope synthesis of γ-acetoxy β-ketoesters.…”