Synthesis of Mono- and Dithiols of Tetraethylene Glycol and Poly(ethylene glycol)s via Enzyme Catalysis

Abstract

This paper investigates the transesterification of methyl 3-mercaptopropionate (MP-SH) with tetraethylene glycol (TEG) and poly(ethylene glycol)s (PEG)s catalyzed by Candida antarctica Lipase B (CALB) without the use of solvent (in bulk). The progress of the reactions was monitored by 1H-NMR spectroscopy. We found that the reactions proceeded in a step-wise manner, first producing monothiols. TEG-monothiol was obtained in 15 min, while conversion to dithiol took 8 h. Monothiols from PEGs with Mn = 1000 and 2050 g/mol were obtained in 8 and 16 h, respectively. MALDI-ToF mass spectrometry verified the absence of dithiols. The synthesis of dithiols required additional fresh CALB and MP-SH. The structure of the products was confirmed by 1H-NMR and 13C-NMR spectroscopy. Enzyme catalysis was found to be a powerful tool to effectively synthesize thiol-functionalized TEGs and PEGs.

NMR Characterization of Polyethylene Glycol Conjugates for Nanoparticle Functionalization

“…Alternatively, the triplets adjacent to the left (δ = 3.82 ppm) and right (δ = 3.47 ppm) of the major peaks have also been assigned to protons b and d . Such assignments ,− are, however, incorrect.…”

“…The most common practice is thus to characterize PEG functionalization with small anchoring moieties by 1 H NMR. − Unfortunately, many published 1 H NMR of functionalized PEGs are incorrectly analyzed without taking into consideration the 13 C– 1 H coupling, which leads to erroneous peak assignments and incorrect quantification of PEG functionalization. Herein, we walk the reader through correct interpretation of 1 H NMR spectra of functionalized PEG.…”

Reversible Aggregation of Covalently Cross-Linked Gold Nanocrystals by Linker Oxidation

“…In contrast, the NCs showed no tendency to redisperse in aqueous MPA (pH 6) at either set of conditions, perhaps because van der Waals attraction between the MPAcapped NCs prevents the NC precipitates from dissolving. While MPA failed to redisperse the NCs, the longer-chain thiol acids MUDA and MHDA dissolved the NC precipitates to give pink-white emulsions that, upon filtering to remove the 105 After ozonation, the αand β-methylene triplets shift downfield while the ether backbone peak area decreases by ∼15%. The postozonation spectrum is assigned to a mixture of hexa(ethylene glycol) disulfonic acid (HEGDS) and its breakdown products.…”

“…(a) 1 H NMR spectra of a 10 mM solution of HEGDT in pure D 2 O before and after 5 min of ozonation. The HEGDT spectrum shows the expected α-methylene triplet at 2.73 ppm (labeled a), β-methylene triplet at 3.67 ppm (labeled b), and oligo ethylene glycol backbone at 3.70 ppm (labeled c−f), in agreement with the literature 105. After ozonation, the αand β-methylene triplets shift downfield while the ether backbone peak area decreases by ∼15%.…”

Recent Advances on Biocatalysis and Metabolic Engineering for Biomanufacturing

“…Among the research articles presented in this issue, there is a set of studies on enzyme catalysis, which was a powerful tool to effectively synthesize various target products. In more detail, Mulay et al investigated Candida antarctica Lipase B-catalyzed transesterification of methyl 3-mercaptopropionate with tetraethylene glycol (TEG) and poly(ethylene glycol)s (PEG)s to synthesize thiol-functionalized TEGs and TEGs without use of solvent [1]. Joo et al reported the biosynthesis of ω-hydroxydodecanoic acid via whole-cell biotransformations using a novel monooxygenase CYP153AL.m from Limnobacter sp.…”