On the Stereochemical Course of Self‐Replication in Secondary Cycle Sharpless Aminohydroxylation

Abstract

An investigation on a potential asymmetric self-replication process within the secondary cycle of Sharpless asymmetric aminohydroxylation is discussed. The reaction of two model olefins is investigated within this process and two different models for an asymmetric process are discussed. Analysis of the results on the basis of these models and a mathematical description for development of the enantiomeric excesses as a function of olefin conversion lead to the conclusion that for such processes there is no possibility for any inhibitory effect and that asymmetric self-replication in secondary cycle aminohydroxylation reactions is not a feasible process.

Nichtlineare Effekte in der asymmetrischen Katalyse

“…Wenn bei metallorganischen Reaktionen das metallgebundene chirale Auxiliar seine eigene Bildung katalysiert, spricht man von einer templatdirigierten Selbstreplikation 208. 209 Muñiz209b berichtete über eine asymmetrische Selbstreplikation bei der Sharpless‐Aminohydroxylierung von Natriummethacrylat (Schema ) in Gegenwart eines nicht‐enantiomerenreinen Osmiumkomplexes 239 . Sowohl homochirales als auch heterochirales 240 unterliegen einer Hydrolyse in situ, die das Produkt 238 liefert und den Katalysator 239 regeneriert.…”

Synthesis of Small Tripeptide Molecules through a Catalysis Sequence Comprising Metathesis and Aminohydroxylation

“…In view of the generally observed low induction in the step to produce C from B , the formation of diastereomeric mixtures at stage C arises. We previously discussed the impossibility for high stereoselectivity in self‐replication processes of related second‐cycle catalysis and therefore expected the formation of both stereoisomers for the present aminohydroxylation reaction of 3 a – e 18. 19 Such a result is well‐suited for the present purpose of a stereodiversified peptide synthesis.…”

Synthetic methods : Part (ii) Oxidation and reduction methods

“…However, a study by Muniz suggests that this is not a feasible process. 59 In further studies from the same group, it has been shown that carrying out aminohydroxylation under typical Sharpless conditions but with the omission of the chiral ligand can lead to the a-ketoamine, rather than the aminoalcohol, being the major reaction product (Scheme 9). 60 Enantiomerically enriched aminoalcohols can be converted to enantiomerically enriched a-aminoketones using similar conditions.…”