AbstractA synthetic methodology has been developed for peptide bond formation with α‐hydroxmethylserine as the carboxyl or amino component and also for the preparation of homo‐sequences. The key intermediate, O,O‐protected α‐hydroxymethylserine in the form of an isopropylidene derivative, is easily accessible and represents the first example of a heterocyclic Cα,α‐disubstituted amino acid containing an 1,3‐dioxane ring. The use of this intermediate facilitates protection of the sterically hindered amino and carboxyl groups and is advantageous for the coupling and deprotection steps. X‐ray structure determination of Z‐HmS(Ipr)–Ala–OMe revealed that the two crystallographically independent molecules present in the asymmetric unit adopt an S‐shaped conformation. In the one molecule the achiral HmS(Ipr) residue has the torsion angle values (ϕ==61.4°,ψ=40.8°) in the left‐handed helical region of the Ramachandran map, while in the second molecule the negative torsion angles (ϕ=−60.1°, ψ=–44.4°) are associated with the right‐handed helix. © 1998 Europea