Stuart Warren (24 Dec 1938-22 Mar 2020)

Celebrating the life of Stuart Warren.

NADPH oxidase 1 is a novel pharmacological target for the development of an antiplatelet drug without bleeding side effects

Growing evidence supports a central role of NADPH oxidases (NOXs) in the regulation of platelets, which are circulating cells involved in both hemostasis and thrombosis. Here, the use of Nox1^-/- and Nox1^+/+ mice as experimental models of human responses demonstrated a critical role of NOX1 in collagen-dependent platelet activation and pathological arterial thrombosis, as tested in vivo by carotid occlusion assays. In contrast, NOX1 does not affect platelet responses to thrombin and normal hemostasis, as assayed in tail bleeding experiments. Therefore, as NOX1 inhibitors are likely to have antiplatelet effects without associated bleeding risks, the NOX1-selective inhibitor 2-acetylphenothiazine (2APT) and a series of its derivatives generated to increase inhibitory potency and drug bioavailability were tested. Among the 2APT derivatives, 1-(10H-phenothiazin-2-yl)vinyl tert-butyl carbonate (2APT-D6) was selected for its high potency. Both 2APT and 2APT-D6 inhibited collagen-dependent platelet aggregation, adhesion, thrombus formation, superoxide anion generation, and surface activation marker expression, while responses to thrombin or adhesion to fibrinogen were not affected. In vivo administration of 2APT or 2APT-D6 led to the inhibition of mouse platelet aggregation, oxygen radical output, and thrombus formation, and carotid occlusion, while tail hemostasis was unaffected. Differently to in vitro experiments, 2APT-D6 and 2APT displayed similar potency in vivo. In summary, NOX1 inhibition with 2APT or its derivative 2APT-D6 is a viable strategy to control collagen-induced platelet activation and reduce thrombosis without deleterious effects on hemostasis. These compounds should, therefore, be considered for the development of novel antiplatelet drugs to fight cardiovascular diseases in humans.

Sidechain Diversification of Grandifloracin Allows Identification of Analogues with Enhanced Anti-Austerity Activity against Human PANC-1 Pancreatic Cancer Cells

The natural product (+)-grandifloracin is a potent "anti-austerity" agent, able to suppress the ability of various pancreatic cancer cell lines to tolerate conditions of nutrient deprivation. Such anti-austerity agents represent a promising approach to cancer chemotherapy. Here we report the synthesis and biological evaluation of racemic analogues of grandifloracin bearing diverse sidechains, of which two show enhanced potency in comparison with the natural product. Additionally, several unexpected by-products containing modifications of the grandifloracin core were isolated, identified and similarly evaluated for biological activity.

Modified perineal stapled rectal resection with Contour Transtar for full-thickness rectal prolapse

OBJECTIVE

We report a modified technique of perineal proctectomy using a new reloadable curved cutter stapler, the Contour Transtar (Ethicon Endo-Surgery), to treat full-thickness external rectal prolapse.

METHOD

Between May and July 2008 three female patients were treated. All had a full-thickness external rectal prolapse up to 10 cm in length. The prolapse was initially divided by a linear cutter in anterior and posterior flaps, and resection of the prolapse was performed with a Contour Transtar stapler.

RESULTS

There was no mortality or early or late morbidity. Follow-up was 2-4 months. All patients had a bowel movement within 3 days of the operation, oral feeding started immediately and the hospital stay was 5 days in all cases. All patients reported an improvement of constipation and continence.

CONCLUSION

Our procedure may be indicated for full-thickness prolapse with a rectal protrusion up to 10 cm, as it allows a simple resection without any mobilization or dissection of the rectum. The technique is safe, easier and faster to perform than conventional perineal rectosigmoidectomy.

The finding of vascular and urinary anomalies in the harvested kidney for transplantation

INTRODUCTION

In kidney transplantation, anatomical vascular and excretory anomalies may represent causes of failure. Today's surgical techniques have made the most of the organs with anatomic anomalies and iatrogenic injury successfully used for transplantation.

MATERIALS AND METHODS

From January 2000 to June 2006, we harvested 230 kidneys, of including 88 kidneys (20%) with vascular, urinary, or vascular-urinary anomalies; 64 kidneys were implanted and 15 were sent to other transplantation centers. Only 9 kidneys were not appropriate for transplantation.

RESULTS

All patients who received kidneys with the above-mentioned anomalies were carefully examined after the transplantation and short-term and long-term complications were evaluated with respect to controls without anomalies.

DISCUSSION

Renal anatomic anomalies are frequently observed during kidney transplantation and may produce postsurgical complications. However, the presence of these anomalies does not necessarily imply the impossibility of using the kidney for a transplant, especially because of improved surgical techniques. Our experience in transplantation procedures showed that even if kidneys present the above-mentioned anomalies they can still be considered appropriate for transplantation when we perform a correct harvesting/back-table transplant surgery. So vascular and urinary anomalies have to be considered always an incentive to research new surgical solutions and to perform a careful surgical technique.

Stereoselective synthesis of 2,3-difunctionalised thioesters using nucleophilic epoxidation of 1-arylthio-1-nitroalkenes

Stereoselective nucleophilic epoxidation of protected 3-amino and 3-hydroxy-substituted 1-arylthio-1-nitroalkenes, followed by intramolecular capture involving the amino and hydroxyl protecting groups, has led to the formation of isomeric oxazolidinones 5 and 7, and a cyclic carbonate 11. Together with the oxazolidinone precursor anti-alpha-bromo thioester 15a, the absolute and relative stereochemistry of these compounds has been determined by X-ray crystallography.

Difficult vascular conditions in kidney transplantation

The new dialytic and medical therapies have improved the survival of uremic patients and their preservation of a efficacious clinical condition so as to warrant suitability for transplantation, even after a long period of dialysis. In addition, today the use of a "marginal donor" and "marginal kidney" are often used to increase the pool of available organs, so that the surgeon must face more technical difficulties than in the past; anomalies of the donor kidney, harvesting and bench surgery damages, as well as vascular pathologies in the recipient. A review of our 151 renal transplantations from January 1999 to May 2003 showed that it was often possible to overcome these technical difficulties yielding good results. This work sought to demonstrate that neither "marginal donor"/"marginal kidney" used to expand donor pool nor recipient vascular pathologies should be considered transplant contraindications. Knowledge of various technical options and the ability to put them rapidly into practice are necessary to use any organ.

Synthesis of orthogonally protected biaryl amino acid derivatives

The efficient and direct synthesis of protected biaryl amino acids, including dityrosine (50% overall yield over 3 steps), by Negishi cross-coupling of the serine-derived organozinc reagent 4 with iodo- and di-iodobiaryls, is reported. An improved, although still not perfect, diiodination of 2,2'-biphenol has been achieved using NMe3BnICl2-ZnCl2. Protection of phenolic hydroxyl groups as acetates, rather than benzyl ethers, is required for efficient cross-coupling, and evidence for acetyl migration has been observed during debenzylation of a substituted 2-acetoxy-2'-benzyloxybiaryl. Aromatic C-I to C-Cl conversion has been detected as a minor reaction pathway in the palladium-catalyzed coupling of aryl iodide 3b with organozinc reagent 4.

A Formal Total Synthesis of Eleutherobin Using the Ring-Closing Metathesis (RCM) Reaction of a Densely Functionalized Diene as the Key Step: Investigation of the Unusual Kinetically Controlled RCM Stereochemistry

Asymmetric oxyallylation reactions and ring-closing metathesis have been used to synthesize compound 3, a key advanced intermediate used in the total synthesis of eleutherobin reported by Danishefsky and co-workers. The aldehyde 6, which is readily prepared from commercially available R-(-)-carvone in six steps in 30 % overall yield on multigram quantities, was converted into the diene 5 utilizing two stereoselective titanium-mediated Hafner-Duthaler oxyallylation reactions. The reactions gave the desired products (8 and 12) in high yields (73 and 83 %, respectively) as single diastereoisomers, with the allylic alcohol already protected as the p-methoxyphenyl (PMP) ether, which previous work has demonstrated actually aids ring-closing metathesis compared to other protective groups and the corresponding free alcohol. Cyclization under forcing conditions, using Grubbs' second-generation catalyst 13, gave the ten-membered carbocycle (E)-14 in 64 % yield. This result is in sharp contrast to similar, but less functionalized, dienes, which have all undergone cyclization to give the Z stereoisomers exclusively. A detailed investigation of this unusual cyclization stereochemistry by computational methods has shown that the E isomer of the ten-membered carbocycle is indeed less thermodynamically stable than the corresponding Z isomer. In fact, the selectivity is believed to be due to the dense functionality around the ruthenacyclobutane intermediate that favors the trans-ruthenacycle, which ultimately leads to the less stable E isomer of the ten-membered carbocycle under kinetic control. During the final synthetic manipulations the double bond of enedione (E)-16 isomerized to the more thermodynamically stable enedione (Z)-4, giving access to the advanced key-intermediate 3, which was spectroscopically and analytically identical to the data reported by Danishefsky and co-workers, and thereby completing the formal synthesis of eleutherobin.

New routes to β-cycloalkylalanine derivatives using serine-derived organozinc reagents

Two distinct routes to beta-cycloalkylalanine derivatives have been developed. The first route employs the reaction of the iodoalanine-derived zinc-copper reagent 2 with cycloalk-1-en-3-yl phosphates, and the second uses the palladium-catalysed coupling of the iodoalanine-derived zinc reagent 1 with cycloalkenyl triflates; in each case, catalytic hydrogenation of the unsaturated product leads to the protected beta-cycloalkylalanine. The latter route allows access to a range of cycloalkyl derivatives, with ring sizes of 5-8. beta-(1-Methyl-1-cyclohexyl)alanine may be prepared using reaction of the zinc-copper reagent 2 with 3-methyl-2-cyclohexenyl chloride, followed by hydrogenation. The corresponding cyclopentyl derivative may be prepared by reaction of the same zinc-copper reagent 2 with diethyl geranylphosphate, followed by ring-closing metathesis and hydrogenation.

Suboptimal kidney: the experience of a single transplant unit

Not all kidneys are suitable for transplantation. In 2001 in Italy, only 1530 of 1748 organs were transplanted. This difference (-12.5%) not only represents organs harvested from marginal donors considered not suitable, but also kidneys that, although collected from standard donors, had a vascular, parenchymal, or urologic anomaly that made them unsuitable for transplantation. In our center, we established a procedure that defined the characteristics of suboptimal kidneys and allowed us to specifically select the appropriate recipient. We considered as suboptimal all organs with complex arterial anomalies (more than 2 arteries although on a single patch or separated such as to need a double anastomosis or a bench reconstruction); organs with noticeable parenchymal damage (macroscopic sclerosis areas or sutured polar branches accidentally damaged during removal), and organs with complex anomalies of the excretory tract (complete double district). The organs were not considered as suboptimal if they had venous anomalies revised on the bench or if they had a double artery with a single patch <2.5 cm. Such organs were transplanted to recipients who were between 55 and 60 years of age with a body weight of at least 20% less than the donor, and female.