Normal Ileal Mucus Is Inadequate for Epithelial Protection in Ileal Pouch Mucosa.

BACKGROUND: Clinical, nonspecific pouchitis is common after restorative proctocolectomy for ulcerative colitis, but its cause is unknown. A possible lack of protection for the ileal mucosa in its role as a reservoir for colonic-type bacteria may be the missing piece in defining the causes of pouchitis. OBJECTIVE: The study aimed to review the causes of pouchitis and introduce the hypothesis that inadequate mucus protection in the pouch, combined with a predisposition to abnormal inflammation, is the most common cause of nonspecific pouchitis. DATA SOURCES: Review of PubMed and MEDLINE for articles discussing pouchitis and intestinal mucus. STUDY SELECTION: Studies published from 1960 to 2023. The main search terms were "pouchitis," and "intestinal mucus," whereas Boolean operators were used with multiple other terms to refine the search. Duplicates and case reports were excluded. MAIN OUTCOME MEASURES: Current theories about the cause of pouchitis, descriptions of the role of mucus in the physiology of intestinal protection, and evidence of the effects of lack of mucus on mucosal inflammation. RESULTS: The crossreference of "intestinal mucus" with "pouchitis" produced 9 references, none of which discussed the role of mucus in the development of pouchitis. Crossing "intestinal mucus" with "pouch" resulted in 32 articles, combining "pouchitis" with "barrier function" yielded 37 articles, and "pouchitis" with "permeability" yielded only 8 articles. No article discussed the mucus coat as a barrier to bacterial invasion of the epithelium or mentioned inadequate mucus as a factor in pouchitis. However, an ileal pouch produces a colonic environment in the small bowel, and the ileum lacks the mucus protection needed for this sort of environment. This predisposes pouch mucosa to bacterial invasion and chronic microscopic inflammation that may promote clinical pouchitis in patients prone to an autoimmune response. LIMITATIONS: No prior studies address inadequate mucus protection and the origin of proctitis. There is no objective way of measuring the autoimmune tendency in patients with ulcerative colitis. CONCLUSIONS: Studies of intestinal mucus in the ileal pouch and its association with pouchitis are warranted.

Stereoselective two-carbon ring expansion of allylic amines via electronic control of palladium-promoted equilibria.

General methodologies enabling the two-carbon homologation of pyrrolidine and piperidine systems have yet to be developed. Herein we report that palladium-catalysed allylic amine rearrangements enable efficient two-carbon ring expansion of 2-alkenyl pyrrolidine and piperidines to their azepane and azocane counterparts. Conditions are mild, tolerant of a range of functional groups and the process can occur with high enantioretention. The products formed undergo a range of orthogonal transformations, making them ideal scaffolds for the creation of compound libraries.

Pd-Catalyzed Cascade Reactions of Aziridines: One-Step Access to Complex Tetracyclic Amines.

The combination of palladium catalysis and thermal cycloaddition is shown to transform tricyclic aziridines into complex, stereodefined tetracyclic products in a single step. This highly unusual cascade process involves a diverted Tsuji-Trost sequence leading to a surprisingly facile intramolecular Diels-Alder reaction. The starting materials are accessible on multigram scales from the photochemical rearrangement of simple pyrroles. The tetracyclic amine products can be further elaborated through routine transformations, highlighting their potential as scaffolds for medicinal chemistry.

Rapid Access to Azabicyclo[3.3.1]nonanes by a Tandem Diverted Tsuji-Trost Process.

A three-step synthesis of the 2-azabicyclo[3.3.1]nonane ring system from simple pyrroles, employing a combined photochemical/palladium-catalysed approach is reported. Substrate scope is broad, allowing the incorporation of a wide range of functionality relevant to medicinal chemistry. Mechanistic studies demonstrate that the process occurs by acid-assisted C-N bond cleavage followed by ß-hydride elimination to form a reactive diene, demonstrating that efficient control of what might be considered off-cycle reactions can result in productive tandem catalytic processes. This represents a short and versatile route to the biologically important morphan scaffold.

Using Nature's polyenes as templates: studies of synthetic xanthomonadin analogues and realising their potential as antioxidants.

Two truncated analogues of the polyenyl photoprotective xanthomonadin pigments have been synthesised utilising an iterative Heck-Mizoroki (HM)/iododeboronation cross coupling approach and investigated as models of the natural product photoprotective agents in bacteria. Despite the instability of these types of compounds, both analogues proved to be sufficiently stable to allow isolation, spectroscopic analysis and biological studies of their photoprotective behaviour which showed that despite their shorter polyene chain length, they retained the ability to protect bacteria from photochemical damage; i.e. incorporation of one compound into E. coli provided photoprotective activity against singlet oxygen analogous to the natural photoprotective mechanisms employed by Xanthomonas bacteria, answering key questions about what minimal functionality is required to impart photoprotection, potentially leading to new classes of photoprotective and antioxidants compounds.

A Rapid Synthetic Approach to the ABCD Core of the Stemona Alkaloids.

A new Lewis acid-assisted Brønsted acid cascade approach for the stereoselective formation of the tetracyclic Stemona alkaloid skeleton is described in five steps from epoxide 15. Crucially, this tetracyclic product can be accessed as either C13 epimer, potentially serving as intermediates for the synthesis of a range of Stemona alkaloids.

Conformationally Driven Two- and Three-Photon Cascade Processes in the Stereoselective Photorearrangement of Pyrroles.

A TBSO group has been shown to exert a high degree of stereocontrol during the two-photon photocycloaddition/rearrangement of N-butenylpyrroles to complex tricyclic aziridines. Moreover, this and other bulky groups have been shown to change the outcome of the reaction, promoting a new two-photon sequence to tricyclic imines and an unprecedented stereoselective three-photon sequence to azabicyclo[3.3.1]nonanes.

Real-Time Biological Annotation of Synthetic Compounds.

Organic chemists are able to synthesize molecules in greater number and chemical complexity than ever before. Yet, a majority of these compounds go untested in biological systems, and those that do are often tested long after the chemist can incorporate the results into synthetic planning. We propose the use of high-dimensional "multiplex" assays, which are capable of measuring thousands of cellular features in one experiment, to annotate rapidly and inexpensively the biological activities of newly synthesized compounds. This readily accessible and inexpensive "real-time" profiling method can be used in a prospective manner to facilitate, for example, the efficient construction of performance-diverse small-molecule libraries that are enriched in bioactives. Here, we demonstrate this concept by synthesizing ten triads of constitutionally isomeric compounds via complexity-generating photochemical and thermal rearrangements and measuring compound-induced changes in cellular morphology via an imaging-based "cell painting" assay. Our results indicate that real-time biological annotation can inform optimization efforts and library syntheses by illuminating trends relating to biological activity that would be difficult to predict if only chemical structure were considered. We anticipate that probe and drug discovery will benefit from the use of optimization efforts and libraries that implement this approach.

Unusually Facile Thermal Homodienyl-[1,5]-Hydrogen Shift Reactions in Photochemically Generated Vinyl Aziridines.

A range of photochemically generated tri- and tetracyclic vinyl aziridines have been found to undergo a general and surprisingly low temperature ring opening through a [1,5]-hydrogen shift reaction. The rate of the process was found to be highly dependent on the structure and substitution around the azirdine ring and the alkene terminus, with some substrates being observed to undergo ring opening at temperatures as low as 25 °C. The rigid nature of these polycyclic systems precludes a conformational explanation of these rate differences, and an Eyring study confirmed a negligible entropic barrier to the reaction. However, the Eyring plots for two different aziridines systems showed a significant difference in their enthalpies of activation. It is therefore believed that the levels of aziridine ring strain, as well as electronic effects, are the dominant factors in this sequence.

Combining photochemistry and catalysis: rapid access to sp3 - rich polyheterocycles from simple pyrroles.

Use of FEP flow reactor technology allows access to gram quantities of photochemically-generated tricyclic aziridines. These undergo a range of novel palladium-catalyzed ring-opening and cycloaddition reactions, likely driven by their inherent strain, allowing incorporation of further functionality by fusing additional heterocyclic rings onto these already complex polycyclic cores. This rapid, 2-step access to complex sp3 - rich heterocycles should be of interest to those in the fields of drug discovery and natural product synthesis.

Heck-Mizoroki coupling of vinyliodide and applications in the synthesis of dienes and trienes.

Vinyliodide reacts chemoselectively under Heck-Mizoroki conditions with terminal alkenes, including vinylboronate esters, to give dienes. The resulting dienylboronates undergo Suzuki-Miyaura couplings with aryl, heteroaryl and alkenyl halides to access dienes and trienes.

Batch versus flow photochemistry: a revealing comparison of yield and productivity.

The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20% lower than that of batch, whereas three-layer reactors were 20% more productive. Finally, the utility of flow chemistry was demonstrated in the scale-up of the ring-opening reaction of a potentially explosive [1.1.1] propellane with butane-2,3-dione.

Design and biological evaluation of synthetic retinoids: probing length vs. stability vs. activity.

All trans-retinoic acid (ATRA) is widely used to direct the differentiation of cultured stem cells. When exposed to the pluripotent human embryonal carcinoma (EC) stem cell line, TERA2.cl.SP12, ATRA induces ectoderm differentiation and the formation of neuronal cell types. We report in this study that novel polyene chain length analogues of ATRA require a specific chain length to elicit a biological responses of the EC cells TERA2.cl.SP12, with synthetic retinoid AH61 being particularly active, and indeed more so than ATRA. The impacts of both the synthetic retinoid AH61 and natural ATRA on the TERA2.cl.SP12 cells were directly compared using both RT-PCR and Fourier Transform Infrared Micro-Spectroscopy (FT-IRMS) coupled with multivariate analysis. Analytical results produced from this study also confirmed that the synthetic retinoid AH61 had biological activity comparable or greater than that of ATRA. In addition to this, AH61 has the added advantage of greater compound stability than ATRA, therefore, avoiding issues of oxidation or decomposition during use with embryonic stem cells.

Flow photochemistry: Old light through new windows.

Synthetic photochemistry carried out in classic batch reactors has, for over half a century, proved to be a powerful but under-utilised technique in general organic synthesis. Recent developments in flow photochemistry have the potential to allow this technique to be applied in a more mainstream setting. This review highlights the use of flow reactors in organic photochemistry, allowing a comparison of the various reactor types to be made.

Endothelin-1 stimulates colon cancer adjacent fibroblasts.

Endothelin-1 (ET-1) is produced by and stimulates colorectal cancer cells. Fibroblasts produce tumour stroma required for cancer development. We investigated whether ET-1 stimulated processes involved in tumour stroma production by colonic fibroblasts. Primary human fibroblasts, isolated from normal tissues adjacent to colon cancers, were cultured with or without ET-1 and its antagonists. Cellular proliferation, migration and contraction were measured. Expression of enzymes involved in tumour stroma development and alterations in gene transcription were determined by Western blotting and genome microarrays. ET-1 stimulated proliferation, contraction and migration (p < 0.01 v control) and the expression of matrix degrading enzymes TIMP-1 and MMP-2, but not MMP-3. ET-1 upregulated genes for profibrotic growth factors and receptors, signalling molecules, actin modulators and extracellular matrix components. ET-1 stimulated colonic fibroblast cellular processes in vitro that are involved in developing tumour stroma. Upregulated genes were consistent with these processes. By acting as a strong stimulus for tumour stroma creation, ET-1 is proposed as a target for adjuvant cancer therapy.

Studies towards the synthesis of the northern polyene of viridenomycin and synthesis of Z-double bond analogues.

Viridenomycin is a structurally challenging, potentially biologically valuable molecule which has yet to succumb to total synthesis. Its instability, perhaps particularly associated with the northern polyene may contribute to the difficulties of piecing this molecule together. The synthesis of northern polyene models, including potentially stabilised analogues incorporating benzene rings as Z-alkene replacements, have been prepared using an efficient series of cross-coupling reactions. The resulting polyenes and polyene surrogates have been converted into tetraene ester and amide models of the viridenomycin system. These analogues have sufficient stability compared with the unsubstituted northern polyene analogue to be viable for future developing a strategy for the construction of viridenomycin and analogues.

A novel, efficient, diastereo- and enantioselective Mukaiyama aldol-based synthesis of a vinyl cyclopentanone core derivative of viridenomycin.

A strategy has been developed for a rapid seven-step construction of a chiral, nonracemic vinyl cyclopentanone building block as part of a synthetic approach to viridenomycin, using a diastereo- and enantioselective Mukaiyama aldol and intramolecular Knoevenagel condensation as key steps.

Mechanistic studies on the Heck-Mizoroki cross-coupling reaction of a hindered vinylboronate ester as a key approach to developing a highly stereoselective synthesis of a C1-C7 Z,Z,E-triene synthon for viridenomycin.

Mechanistic studies of the Heck-Mizoroki reaction of a vinylboronate ester with electronically different (four-substituted) aryl iodides shows that electron donors accelerate the cross-coupling, demonstrating that the oxidative addition step is not rate determining and that there is development of some degree of positive charge in the rate determining step. These results were used as a basis to allow the development of reaction conditions for the Heck-Mizoroki coupling of a hindered vinylboronate ester with electron deficient methyl cis-2-iodoacrylate. The resulting dienylboronate ester was converted through a series of highly stereoselective iodo-deboronations and Heck-Mizoroki reactions into a trienyl iodide precursor for further application in the total synthesis of viridenomycin.

The Heck-Mizoroki cross-coupling reaction: a mechanistic perspective.

The Heck-Mizoroki cross-coupling reaction is an important part of the synthetic chemist's toolbox, and it has been applied to a huge variety of different substrates. In contrast, the mechanism of the process is much less studied, and consequently less understood. There have been numerous studies reported over recent years, both experimental and theoretical, aimed at uncovering the inner working of this palladium-mediated coupling process. This perspective aims to review and compare these works and to provide an up-to-date view of this reaction.