✍ Scribed by Enders, Dieter ;Wiedemann, Jürgen
No coin nor oath required. For personal study only.
The stereoselective conjugate addition of (S)‐(–)‐1‐(trimethylsilylamino)‐2‐(methoxymethyl)pyrrolidine (TMS‐SAMP) to ω‐halide‐substituted α,β‐unsaturated esters 1 is utilized to prepare carbocyclic and heterocyclic β‐amino acids 2 and 5 of high diastereo‐ and enantiomeric purity via the corresponding β‐hydrazino esters by selective intramolecular alkylation of the intermediate ester enolate or the hydrazino moiety. The auxiliary is removed by reductive NN bond cleavage. The stereochemistry of the resulting trans‐2‐aminocycloalkanecarboxylic acids (2) and azacycloalk‐2‐ylacetic acid esters (5) is confirmed by NMR spectroscopy and polarimetry. A transition‐state model for the highly diastereoselective conjugate addition of TMS‐SAMP to enoates is presented.
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## Michael addition / Nitro alkenes / C-O bond cleavage The first intermolecular asymmetric oxa Michael additions cleavage of the auxiliary occurred without epimerisation (69-99%) using Na/NH 3 . The Boc-protected 2-amino alcohols with removable chirality information within the hydroxide source ar