New Hydrophobic Vitamin B12 Derivatives via Ring-Opening Reactions of c-Lactone

The inorganic chemistry of the cobalt corrinoids - an update

The inorganic chemistry of the cobalt corrinoids, derivatives of vitamin B₁₂, is reviewed, with particular emphasis on equilibrium constants for, and kinetics of, their axial ligand substitution reactions. The role the corrin ligand plays in controlling and modifying the properties of the metal ion is emphasised. Other aspects of the chemistry of these compounds, including their structure, corrinoid complexes with metals other than cobalt, the redox chemistry of the cobalt corrinoids and their chemical redox reactions, and their photochemistry are discussed. Their role as catalysts in non-biological reactions and aspects of their organometallic chemistry are briefly mentioned. Particular mention is made of the role that computational methods - and especially DFT calculations - have played in developing our understanding of the inorganic chemistry of these compounds. A brief overview of the biological chemistry of the B₁₂-dependent enzymes is also given for the reader's convenience.

Amide Derivatives of Ginkgolide B and Their Inhibitory Effects on PAF-Induced Platelet Aggregation

Ginkgolides are the most important components of Ginkgo biloba extracts, whose lactone can be hydrolyzed in the aqueous environment. Although the hydrolyzed products have complex structures and their functions are not well-understood, opening the lactone ring is an important strategy in producing novel derivatives of ginkgolide. The preparation of a single pure aminolyzed ginkgolide for the study of its bioactivity and understanding of the process of aminolysis are challenging. To obtain stable aminolyzed products, four amide derivatives (2-5) of ginkgolide B (GB, 1) were prepared via the ring-opening reaction of its lactone with propylamine. These products were purified and fully identified by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy and were further evaluated for their ability to inhibit the PAF-induced platelet aggregation of rabbit platelets in vitro. Compound 2, which was obtained by selective aminolysis of the lactone ring C of GB, showed a much better inhibitory activity of platelet aggregation (IC₅₀, 15 nM) than the parent compound GB (IC₅₀, 442 nM). The other three products (3-5), which were obtained by the aminolysis of lactone rings C and F of GB, did not show platelet aggregation inhibitory activity. The results greatly extended our understanding of the chemistry of GB and provided important structural information for the exploration and development of new drugs based on ginkgolides in G. biloba.

Small alterations in cobinamide structure considerably influence sGC activation

Specially designed B-ring-modified cobalamin derivatives were synthesized and tested as potential activators of soluble guanylyl cyclase (sGC). Herein, we disclose the influence of substituents at the c- and d-positions in hydrophilic and hydrophobic cobyrinic acid derivatives on their capacities to activate sGC. The presence of the amide group at c-/d-position in cobyrinic acid derivatives strongly influence the level of sGC activation. Removal of the d-position altogether has a profound effect for hydrophobic compounds. In contrast, little differences were observed in hydrophilic ones.

Protoporphyrin IX/Cobyrinate Derived Hybrids - Novel Activators of Soluble Guanylyl Cyclase

A new cobyrinate/protoporphyrin IX molecular hybrids were prepared via CuAAC reaction. The synthesis involved selective preparation of cobyrinate and PpIX derived building blocks possessing respectively terminal alkyne and azide moieties followed by the CuOAc catalyzed cycloaddition reaction. Synthesized molecules activated soluble guanylyl cyclase showing strong linker length/activation dependence.

Vitamin B₁₂ derivatives as activators of soluble guanylyl cyclase

Various newly prepared and previously known vitamin B₁₂ derivatives have been studied as potential soluble guanylyl cyclase (sGC) activators. All compounds tested were found to activate the sGC enzyme, although to differing extents. The best results were obtained with the derivatives synthesized from c-lactone and possessing aliphatic amides in the c- and d-positions.

Synthesis of New Hydrophilic and Hydrophobic Cobinamides as NO-Independent sGC Activators

Herein, the synthesis of novel hydrophobic and hydrophilic cobinamides via aminolysis of vitamin B12 derivatives that activate soluble guanyl cyclase (sGC) is presented. Unlike other sGC regulators, they target the catalytic domain of sGC and show higher activity than (CN)2Cbi.

One-step synthesis of α/β cyano-aqua cobinamides from vitamin B12 with Zn(II) or Cu(II) salts in methanol

This short communication describes the screening of various metal salts for the preparation of cyano-aqua cobinamides from vitamin B12 in methanol. ZnCl2 and Cu(NO3)2·3H2O have been identified as most active for this purpose and represent useful alternatives to the widely applied Ce(III) method that requires excess cyanide.