Synthesis of amphiphilic copolymer having acid-labile bicyclo bisoxazolidine in the side chain for controlled release of fragrance aldehyde

The total synthesis of the octacosapeptide corresponding to the proposed primary structure of porcine somatostatin-28, a possible precursor of somatostatin, is described. The primary structure of somatostatin-28 corresponds to that of somatostatin elongated at the N-terminus by a tetradecapeptide sequence. The synthesis has been performed using the strategy of overall acid labile side chain protection based on tert-butanol and adamantol derived protecting groups in combination with the S-tert-butylthio group for the reversible blocking of the cysteine thiol functions and the Nα -2-nitrophenylsulfenyl group for the chain elongation steps. Upon assembly in sequence order of the four suitably protected fragments related to sequence 18-28, 15-17, 8-14 and 1-7, respectively, reductive cleavage of the S-tert-butylthio groups from the fully protected octacosapeptide, followed by acidolytic deprotection via exposure to trifluoroacetic acid and subsequent air oxidation led to crude somatostatin-28. Purification by gel filtration on Biogel P 6 and ion exchange chromatography on Biogel CM 2 produced the desired product in satisfactory yields and at a high degree of purity as judged from different analytical tests. The correctness of the proposed primary structure was ultimately proofed by comparative analysis of the synthetic and natural product by means of chromatographic, immunological and biological assays

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Synthesis of 2-hydroxy-3-isopropoxypropyl guar gum and its thermo-responsive property for controlled release

BioResources ◽

10.15376/biores.15.4.7615-7627 ◽

2020 ◽

Vol 15 (4) ◽

pp. 7615-7627

Author(s):

Ye Tian ◽

Yue Shang ◽

He Ma ◽

Ying Liu

Keyword(s):

Controlled Release ◽

Self Assembly ◽

Guar Gum ◽

Glycidyl Ether ◽

Nile Red ◽

Solution Temperature ◽

Side Chain ◽

Hydrophobic Region ◽

Transmission Electron ◽

Assembly Behavior

2-Hydroxy-3-isopropoxypropyl guar gum (HIPGG), which is a novel polysaccharide-based thermo-responsive polymer, was synthesized via grafting a hydrophobic reagent (isopropyl glycidyl ether (IPGE)) onto a hydrophilic main backbone (guar gum (GG)). The HIPGG exhibited reversible and tunable thermo-responsive properties. Changing the molar substitution (MS) of the hydrophobic side chain enabled the lower critical solution temperature (LCST) to be adjusted within the range of 29.6 °C to 43.7 °C. Fluorescence spectrometry, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to investigate the self-assembly behavior of HIPGG and the thermo-dependent size of its aggregates. It was demonstrated that HIPGG formed stable aggregates in aqueous solution, and the diameters of the aggregates increased as temperature increased. Subsequently, Nile red was used as a model to investigate the encapsulation and temperature-controlled release behaviors in HIPGG aggregates. The results indicated that Nile red was easily encapsulated in the hydrophobic region of HIPGG aggregates, and its release at 36 °C, 38 °C, and 42 °C revealed that temperature had a remarkable impact on release behavior.

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