Metathesis-based linker

A report8 by the Seeberger group introduced a cross-metathesis-based linker (Scheme 4.10). 

Scheme 4.9 A ring-closing metathesis-based linker. 

Knerr L, Schmidt RR. Application of a ring closing metathesis based linker to the solid phase synthesis of oligosaccharides. Synlett 1999 1802-1804. 

Cleavage of polymer-bound allyl esters with palladium catalysts provides general access to 7i-allyl complexes, which can react with a variety of nucleophiles. This has been used in the development of re-allyl-based linkers. Ene-yne cross metathesis and subsequent cleavage in the presence of different nucleophiles yields the corresponding functionalized dienes 93 [93] (Scheme 6.1.19). 

Fully protected tumor-associated carbohydrate antigen Globo-H (50), a potential breast and prostate cancer vaccine [54, 55], was assembled by automated solid support synthesis using oct-4-ene-l,8-diol linker 49 and building blocks 51-56 (Scheme 20.15). The linker is stable to acid and base but is cleaved cleanly by olefin metathesis [56]. The octenediol linker performs best on Merrifield s PS resin, affording routinely loadings in a range of 0.1-0.3 mmol g 1. 

Norbornenyl functionalised linseed oil and cyclopentadiene oligomer-based thermosetting resins have been successfully synthesised using dicy-clopentadiene or other polycyclic norbornene-based comonomers as cross-linkers. New biorenewable-based thermosets have been successfully synthesised by the ring opening metathesis polymerisation of norbornenyl functionalised fatty alcohols of soybean and castor oils. The castor oil-based thermoset exhibits lower soluble fractions and higher thermal stability and mechanical properties compared with the soybean oil-based thermoset. This is due to more effective cross-linking. ... 

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