Preparation and Reactions of Stannylated Amino Acids

Abstract

Hydrostannations of propargylic glycine esters with the new hydrostannation catalyst [Mo(CO)3(CNtBu)3] (MoBI3) gave rise to alpha-stannylated allylic esters in good yield and with high regioselectivity. The chelate Claisen rearrangements of these esters allow the syntheses of gamma,delta-unsaturated amino acids with a vinylstannane moiety in the side chain. The amino acids obtained can be further modified by cross-coupling with various types of electrophiles.

cineSubstitution and the Cu Effect in Stille Cross‐Coupling Reactions: Mechanistic Perspectives and Synthetic Utility

“…Treatment of the (tributylstannyl)allylglycine derivative 6 (Scheme ) with various unsaturated halides or pseudohalides with catalysis by Pd 0 provided an alternative means of access to elaboration of the side chains of non‐proteinogenic α‐amino acids 8a. However, after considerable experimentation (variation of Pd 0 source, ligand, additive, and solvents), there were always some cine substitution products 7 c as E / Z mixtures together with the desired ipso substitution products 7 i , a situation also encountered in Kazmaier's similar work 8b. It is interesting to note the effect that the electron densities on the aryl groups have on the ipso / cine ratios of the Stille reactions.…”

Synthesis of Chlamydocin by Chelate‐Claisen Rearrangement

“…[22] Our group is also involved in amino acid and peptide synthesis, investigating reactions of metal-chelated enolates. [23] These enolates are excellent nucleophiles for transition-metal-catalyzed allylic alkylations, [24] giving rise to γ,δunsaturated amino acids. The same structural motif can be obtained through a chelate-enolate Claisen rearrangement, [25] an approach well suited for highly functionalized amino acids [26] and peptides.…”

Thiol‐Ene Click Reactions – Versatile Tools for the Modification of Unsaturated Amino Acids and Peptides

“…[19] Besides Pd catalysts, complexes of Rh [20] and Ru [21] can be used in the allylic alkylations. [23] To increase the potential of γ,δ-unsaturated amino acids even more, we became interested in their thiol-ene click reactions. [22] If stannylated substrates are used, the metallated amino acid formed can be subjected to subsequent crosscoupling reactions to generate libraries of structurally related amino acids and peptides.…”