Poly orthoesters preparation

Schuerch2) reviewed the medical application of synthetic poly-saccharides. Capozza199 reported that the poly-orthoester prepared from 2-ethoxy-4-hydroxymethyl-l,3-diox-olane in the presence of add are useful as slow-release agents for drugs. Poly-2,6,7-trioxabicyclo[2.2.1]heptane VIII showed the same behavior200). 

Incorporation of the tetrahydrofuran ring into condensation polymers has been accomplished (79USP4180646) by transesterification of orthoester (43) with polyols to prepare poly (orthoesters) (44 Scheme 11). This polymerization reaction has been extended to a wide variety of other orthoester and orthocarbonate starting materials. The product polymers are reported to be excellent biodegradable matrices for drug delivery. 

Finally, poly(orthoesters) may be prepared (79USP4136252) from monomers such as 2-ethoxy-4-hydroxymethyl-1,3-dioxolane (91 Scheme 25), and find use in areas such as controlled release of drugs and other beneficial agents due to their slow and controlled degradation in aqueous biological environments. 

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