Synthesis of cyclic dimeric methyl morpholinoside—a common synthetic precursor to cyclic dinucleotide analogs

Synthesis of Morpholino Nucleosides Starting From Enantiopure Glycidol

A protocol for the synthesis of modified morpholino monomers was performed in few steps through the condensation between 6-hydroxymethyl-morpholine acetal and nucleobases under Lewis acid conditions. The key common precursor...

A Click-Chemistry Linked 2'3'-cGAMP Analogue

2'3'-cGAMP is an uncanonical cyclic dinucleotide where one A and one G base are connected via a 3'-5' and a unique 2'-5' linkage. The molecule is produced by the cyclase cGAS in response to cytosolic DNA binding. cGAMP activates STING and hence one of the most powerful pathways of innate immunity. cGAMP analogues with uncharged linkages that feature better cellular penetrability are currently highly desired. Here, the synthesis of a cGAMP analogue with one amide and one triazole linkage is reported. The molecule is best prepared via a first Cu^I -catalyzed click reaction, which establishes the triazole, while the cyclization is achieved by macrolactamization.

Clarifying the Equilibrium Speciation of Periodate Ions in Aqueous Medium

Equilibria of periodate ion were reinvestigated in aqueous solution by using potentiometric titration, UV and Raman spectroscopies, and gravimetry simultaneously at 0.5 M ionic strength and at 25.0 ± 0.2 °C. Stepwise acid dissociation constants of orthoperiodic acid were found to be pK₁ = 0.98 ± 0.18, pK₂ = 7.42 ± 0.03, and pK₃ = 10.99 ± 0.02, as well as pK₂ = 7.55 ± 0.04 and pK₃ = 11.25 ± 0.03 in the presence of sodium nitrate and sodium perchlorate as background salts, respectively. pK₁ cannot be determined unambiguously from our experiments in the presence of sodium perchlorate. The molar absorptivity spectrum of H₄IO₆^- and H₃IO₆^2- was determined in the range of 215-335 nm, as major species of periodate present from slightly acidic to slightly alkaline conditions. The solubility of periodate decreases significantly under alkaline conditions, and it was determined to be (2.8 ± 0.4) mM by gravimetry, under our experimental conditions. None of these studies gave any clear evidence for an ortho-meta equilibrium and the frequently invoked dimerization of periodate. All measurements can quantitatively be described by the presence of orthoperiodic acid and its three successive deprotonation steps.

A novel application of the Staudinger ligation to access neutral cyclic di-nucleotide analog precursors via a divergent method

Our efforts to develop a scalable and divergent synthesis of cyclic di-nucleotide analog precursors have resulted in (1) an orthogonally protected di-amino carbohydrate as well as (2) the novel application of the Staudinger ligation to provide medium-sized macrocycles featuring carbamate or urea linkages.

Cyclic dinucleotide (c-di-GMP, c-di-AMP, and cGAMP) signalings have come of age to be inhibited by small molecules

Bacteria utilize nucleotide-based second messengers to regulate a myriad of physiological processes. Cyclic dinucleotides have emerged as central regulators of bacterial physiology, controlling processes ranging from cell wall homeostasis to virulence production, and so far over thousands of manuscripts have provided biological insights into c-di-NMP signaling. The development of small molecule inhibitors of c-di-NMP signaling has significantly lagged behind. Recent developments in assays that allow for high-throughput screening of inhibitors suggest that the time is right for a concerted effort to identify inhibitors of these fascinating second messengers. Herein, we review c-di-NMP signaling and small molecules that have been developed to inhibit cyclic dinucleotide-related enzymes.