Hexyl-modified morpholine-2,5-dione-based oligodepsipeptides with relatively low glass transition temperature

An Optimized and Universal Protocol for the Synthesis of Morpholine-2,5-Diones from Natural Hydrophobic Amino Acids and Their Mixture

Morpholine-2,5-diones (MDs) are increasingly attractive compounds that can be produced using amino acid (AA) as a starting material. These compounds can undergo polymerization to produce biodegradable materials, namely, polydepsipeptides, that hold the potential to be used in medicinal applications. In this study, a simplified yet high-yield MD synthesis procedure was developed and applied to produce a range of MDs derived from hydrophobic AAs including Leu, Ile, Val, Phe, Asp(OBzl), Lys(Z), and Ser(tBu). Moreover, using a blend of hydrophobic amino acids (Leu, Ile, Val, and Phe), mixtures of MDs could be synthesized simultaneously. Finally, the polymerization of these MD mixtures was probed and proven successful. The concept investigated herein constitutes a novel path toward the valorization of protein-rich waste by producing renewable and biodegradable materials.

Organocatalyzed Ring-Opening Polymerization of (S)-3-Benzylmorpholine-2,5-Dione

A 3-benzylmorpholine-2,5-dione monomer is synthesized from the natural amino acid l-phenylalanine and characterized by means of nuclear magnetic resonance and infrared spectroscopy, electrospray ionization mass spectrometry, and elemental analysis. Subsequent to preliminary polymerization studies, a well-defined poly(ester amide) homopolymer is synthesized via ring-opening polymerization using a binary catalyst system comprising 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and a 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea (TU) cocatalyst with a feed ratio of M/I/DBU/TU = 100/1/1/10. Kinetic studies reveal high controllability of the dispersities and molar masses up to conversions of almost 80%. Analysis by mass spectrometry hints toward excellent end-group fidelity at these conditions. In consequence, utilization of hydroxyl-functionalized poly(ethylene glycol) and poly(2-ethyl-2-oxazoline) as macroinitiators results in amphiphilic block copolymers. Bulk miscibility of the building blocks is indicated by differential scanning calorimetry investigations. As more and more promising new drugs are based on hydrophobic molecules featuring aromatic moieties, the novel polyesteramides seem highly promising materials to be used as potential drug delivery vehicles.

Recent Advances of Poly(ester amide)s-Based Biomaterials

Biodegradable and biocompatible biomaterials have offered much more opportunities from an engineering standpoint for treating diseases and maintaining health. Poly(ester amide)s (PEAs), as an outstanding family among such biomaterials, have risen overwhelmingly in the past decades. These synthetic polymers have easily and widely available raw materials and a diversity of synthetic approaches, which have attracted considerable attention. More importantly, combining the superiorities of polyamides and polyesters, PEAs have emerged with better functions. They could have improved biodegradability, biocompatibility, and cell-material interactions. The PEAs derived from α-amino acids even allow the introduction of pendant sites for further modification or functionalization. Meanwhile, it is gradually recognized that the chemical structures are closely related to the physiochemical and biological properties of PEAs so that their properties can be precisely controlled. PEAs therefore become significant materials in the biomedical fields. This review will attempt to summarize the recent progress in the development of PEAs with respect to the preparation materials and methods, structure-property relationships along with their latest biomedical accomplishments, especially for drug delivery and tissue engineering.

Diketomorpholines: Synthetic Accessibility and Utilization

Diketomorpholines (DKMs; morpholine-2,5-diones) possess a six-membered ring with a lactone and lactam moiety and belong to the family of cyclodepsipeptides. In this review, the synthetic accessibility of DKMs is summarized and their utilization, in particular, for ring-opening polymerization reactions, is highlighted. The occurrence of the DKM scaffold in natural products encompasses small monocyclic compounds but also complex, polycyclic representatives with a fused DKM ring.

Prospects of Using Biocatalysis for the Synthesis and Modification of Polymers

Trends in the dynamically developing application of biocatalysis for the synthesis and modification of polymers over the past 5 years are considered, with an emphasis on the production of biodegradable, biocompatible and functional polymeric materials oriented to medical applications. The possibilities of using enzymes not only as catalysts for polymerization but also for the preparation of monomers for polymerization or oligomers for block copolymerization are considered. Special attention is paid to the prospects and existing limitations of biocatalytic production of new synthetic biopolymers based on natural compounds and monomers from biomass, which can lead to a huge variety of functional biomaterials. The existing experience and perspectives for the integration of bio- and chemocatalysis in this area are discussed.