Selenium‐NMR Spectroscopy in Organic Synthesis: From Structural Characterization Toward New Investigations

Abstract

This review article deals with organic synthesis from the perspective of selenium-77 nuclear magnetic resonance (NMR) spectroscopy. Different types of organic reactions are briefly discussed, incorporating mechanism aspects through 77 Se NMR observable intermediates and byproducts. The 77 Se NMR experiments are demonstrated in terms of structural characterization and new insights for organic reactions. The ability to visualize different molecules in a reaction mixture provides a facile and versatile route for the development of synthetic organoselenium compounds. Thus, the review describes the strategies accomplished mainly in the past five years in the syntheses and applications of the organoselenium compounds, focusing on 77 Se NMR spectroscopy.

Cysteine-Activated Small-Molecule H2Se Donors Inspired by Synthetic H2S Donors

“…We proposed that the reaction of 12 and Cys would generate intermediate 12a and products including H 2 Se, 10 , and 13 (Figure e), which were characterized by 77 Se­{ 1 H} NMR and HPLC. As expected, 12 (90 mM) in DMSO- d 6 exhibited a 77 Se peak (δ = 576 ppm) for selenoamide . During the reaction with Cys, a new 77 Se peak (δ = 250 ppm) was observed (Figure f), which may be assigned to the generation of intermediate selenol 12a .…”

“…From the therapeutic viewpoint and for in vivo applications in H 2 Se-related biological research, ideal H 2 Se donors should be water-soluble and biocompatible compounds that can release H 2 Se slowly under controllable, tunable activation with a clear triggering mechanism . To this end, we shifted to investigate arylselenoamides (Scheme ) because the analogue arylthioamides are water-soluble and reported to be very slowly activated by Cys. , Synthesis of selenobenzamide 5 was facilely achieved by the reaction of WR and benzamide in toluene at 130 °C in a sealed tube for 30 min . To prepare the selenobenzamide derivatives, we treated 4-hydroxybenzonitrile with selenium powder and sodium borohydride to produce 6 , which was further coupled with acetic acid to give 7 .…”

Visible Light‐Mediated Functionalization of Selenocystine‐Containing Peptides

“…Analysis of the LC/MS data showed that the products were seleninic acid 18 and a dehydroalanine (Dha) derivative 20, respectively (Scheme 6). On the basis of 77 Se NMR spectroscopy data [54] (Figure 3A), alkyl seleninic acid 18 (RSeO 2 H 1217.5 ppm, [M + Na] = 471.0633) was formed after 1 h of irradiation. Our attempts to isolate oxidized form of 1 a failed due to product lability.…”

77Se-Enriched Selenoglycoside Enables Significant Enhancement in NMR Spectroscopic Monitoring of Glycan–Protein Interactions

“…77 Se is a spin-1 2 NMR isotope with broad chemical shift range (ca. 3000 ppm), which makes it promising as a selective probe [25,[27][28][29]. Direct 77 Se NMR detection [30,31] is, however, unfavorable owing to the low natural abundance (7.63%) and decreased sensitivity (0.7 of 1 H) of this nucleus.…”