Synthesis of 20- and 25-membered optically pure macrolides by cationic ring-opening oligomerization of 6,8-dioxabicyclo[3.2.1]octan-7-one of lower optical purities

Abstract

Durch kationische Ringöffnungs‐Olig0merisierung des aus dem Dihydropyran (I) erhältlichen bicyclischen Oxalactons (II)/(III), in dem das (S)‐Enantiomere (III) angereichert ist, werden die 20‐ bzw. 25gIiedrigen optisch aktiven reinen Makrocyclen (IV) und (V) synthetisiert.

Synthesis and ring-opening polymerization of bicyclic lactones containing a tetrahydropyran ring. 2,6-Dioxabicyclo[2.2.2]octan-3-one

“…The first is the acyl-oxygen scission (a) of the ester linkage, leading to a cis-disubstituted tetrahydropyran ring (9). The second is the alkyloxygen scission (b) of the ester linkage, which gives a trans-disubstituted tetrahydropyran ring (SN2 type reaction) or a mixture of cis-and trans-disubstituted tetrahydropyran rings (SN1 type reaction) (10). The third is the C(l)-0(6) bond scission (c) giving rise to trans-disubstituted or a mixture of trans-and cis-disubstituted -lactone rings (11), depending on the types of reactions.…”

Expansion of the Concept of Nonlinear Effects in Catalytic Reactions Beyond Asymmetric Catalysis

“…In a seminal study they could demonstrate the influence of these interactions on the outcome of the stereoisomeric distribution of the products of stoichiometric reactions. Related observations followed in subsequent years but the first systematic study using mathematical models to explain the effect of non‐enantiopure substrates on the enantiopurity of the products only emerged in 1985 . The term nonlinear effect (NLE) was later coined by Kagan and co‐workers and was defined as “the nonlinear dependence of the product enantiopurity on the enantiopurity of a chiral auxiliary utilized in either asymmetric catalysis or asymmetric synthesis”.…”

High-Tg PLA copolymers via base-catalyzed transesterification of PLA with 2,5,7-trioxabicyclo[2.2.2]octan-6-one

“…Hall and Okada systematically investigated the ROP of bicyclic lactones. [47][48][49][50][51][52][53][54][55] Recently, several other bicyclic lactones have also been synthesized and polymerized to generate high thermally stable polyesters with good mechanical properties and potential closed-loop recycling of monomers (Scheme 1). [55][56][57][58][59] The ROP of oxygen-containing bicyclic lactones (Scheme 1, VI-VIII) exhibits different polymerization behavior.…”

“…52 The cationic ROP of 6,8-dioxabicyclo[3.2.1]octan-7-one (VIII) could only generate 20- and 25-membered optically pure macrolides. 50 These bicyclic lactones are produced in many steps from non-renewable resources. Since the development of sustainable polymers requires simple and environmentally-friendly monomer synthesis, we propose to prepare new bicyclic lactones containing cyclic acetal/ketal linkages from a one-step reaction of the esterification and acetalization (ketalization) of triols and aldehyde acids (keto acids).…”