Rufomycin and ilamycin are synonymous
for the same class of cyclopeptides,
currently encompassing 33 structurally characterized isolates and
9 semisynthetic derivatives. Elucidation of new structures prioritized
the consolidation of the names and established the structures of four
diastereoisomeric rufomycins with a 2-piperidinone, named rufomycins
4–7, including full 1H/13C NMR assignments.
The characteristic HSQC cross-peak for the CH-5, the hemiaminal carbon
in amino acid #5, allows assignment of the stereocenters C-4 and C-5
within this ring. Semisynthetic derivatives (rufomycinSS 1, 2, and
3) were prepared from a rufomycins 4 and 6 mixture to validate the
structural assignments. Based on the X-ray crystal structures of rufomycins
2 and 4, considering the NMR differences of rufomycins 7 vs 4–6
compared to rufomycinSS 1 vs 2 and 3, and taking into account that
two major conformers, A and B, occur in both rufomycinSS 2 and 3,
structural modeling was pursued. Collectively, this paper discusses
the NMR spectroscopic differences of the stereoisomers and their possible
3D conformers and correlates these with the anti-Mycobacterium
tuberculosis activity. In addition, a look at the history
prioritizes names and numbering schemes for this group of antibiotics
and leads to consolidated nomenclature for all currently known members,
natural and semisynthetic derivatives, and serves to accommodate future
discoveries.
Favipiravir is an established antiviral that is currently being assessed as an investigational drug for the treatment of COVID-19. Favipiravir is strikingly similar to two molecules that the World Health Organization (WHO) lists as essential medicines, which also consist of a six-membered aromatic N-heterocycle bearing a carboxamide function: the anti-tuberculosis agent, pyrazinamide, and nicotinamide, also known as vitamin B 3 . We demonstrate the utility of 1 H nuclear magnetic resonance (NMR) profiling, an emerging pharmacopoeial tool, for the highly specific identification, selective differentiation of congeners, and subsequent detection of drug falsification or adulteration of these medicines. The straightforward comparison of basic 1-D 1 H NMR spectra, obtained with benchtop or advanced NMR instruments alike, offers a rapid identity assay and works independently of physical reference materials. This approach accelerates and advances pharmaceutical quality control measures under situations of increased drug demand and altered economy, such as during a pandemic.
Monoclonal antibody–drug conjugates (ADCs) are
an expanding
therapeutic class of biomolecules for which relatively few analytical
and preparative separation options exist. Purification of ADCs with
a specific drug antibody ratio is even more challenging. We report
the first application of countercurrent separation (CCS) to this problem.
An ADC mimic was successfully chromatographed using an aqueous two-phase
system (ATPS) consisting of PEG 1000/sodium citrate pH 7.5/water,
17.75/17.75/64.50 (w/w/w). Notably, different partition coefficients
(K) in this ATPS for the ADC mimic (0.09 < K < 0.16) and its monoclonal antibody backbone, IgG (0.16
< K < 0.27), were observed using CCS. Differential
elution behavior of such high-molecular-weight biomolecules, 146,441
vs. ∼150,000 Da, using CCS has no precedent. The results provide
a proof of concept for further exploration of the application of ATPSs
and CCS to the separation of ADCs.
In the first phytochemical investigation of Trichuriella monsoniae, three known flavonoidal C-glycosides, isoswertisin 1, 2″-O-β-d-galactosyl isoswertisin 2 and 2″-O-β-d-xylosyl isoswertisin 3 were isolated from the methanolic extract of the whole plant. Their structures were elucidated by extensive NMR spectroscopic studies including 2D NMR and HRMS, and the structure of 2 was supported by single crystal X-ray data studies. Further, NMR assignments for 3 are being reported for the first time.
Turmeric contains three important analogs, curcumin, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), collectively called as curcuminoids. Curcumin, the most abundant of these curcuminoids is reported to have antioxidant, anti-inflammatory, neuroprotective, antimicrobial, nematocidal, antimutagenic, anticarcinogenic, antiretroviral and chemopreventive activities. Curcumin (a symmetric diketone) analogs 3a-e were synthesized fromdiketones and aromatic aldehydes using solid phase microwave irradiation method in presence of boric acid in diethanolamine, acetic acid (1:1) with reduced reaction time and enhanced %yield. Various clays like Alumina (neutral), Silica gel and Montmorillonite K 10 were used as solid phase catalysts where alumina was found to be efficient in the synthesis of curcumin analogs.
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