Oxacarbenium ion intermediates in the stereoselective synthesis of anionic oligosaccharides

In this thesis new strategies towards biologically active oligosaccharides are described. In addition a detailed mechanistic study is performed to investigate the stereodirecting capacity of glycosyl C-5 substituents in systems that were devoid of any other stereodirecting factors. The postulated mechanism described here can aid in the design of glycosylation strategies.UBL - phd migration 201

Unsuccessful Stent Graft Repair of a Hepatic Artery Aneurysm Presenting with Haemobilia:Case Report and Comprehensive Literature Review

AIMS: To discuss treatment strategies for non-traumatic, non-iatrogenic hepatic artery aneurysms (HAAs) in the presence of an arteriobiliary fistula, illustrated by a case and followed by a comprehensive review of the literature. METHODS: Following the PRISMA guidelines, 24 eligible HAA cases presenting with haemobilia were identified. Characteristics of patients, aneurysms, treatment strategies and their outcomes were collected. RESULTS: A 69 year old patient with no previous hepatobiliary intervention or trauma, presented with jaundice and haemobilia caused by a HAA. Initial treatment by endovascular stenting was chosen to prevent ischaemic liver complications. Unfortunately, this strategy failed because of stent migration due to ongoing infection leading to a type 1A endoleak. The patient had to be converted to open surgery with ligation of the HAA. The patient recovered uneventfully and no complications occurred during the following 12 months. COMPREHENSIVE LITERATURE REVIEW: Of the 24 cases, nine had a true HAA and 15 were pseudo/mycotic aneurysms, mainly caused by endocarditis or cholecystitis. The majority were located in the right hepatic artery. In 20 cases, an endovascular first approach was chosen with embolisation, none with covered stents. Three of these cases had to be converted to open surgery because of rebleeding. In all open (primary or secondary) cases, ligation of the HAA was performed. One patient in these series died. No liver ischaemia or abscesses were reported, although one patient developed an ischaemic gallbladder. CONCLUSIONS: Patients who present with a HAA and haemobilia may be treated safely by embolisation or open ligation. Using a covered stent graft in these patients can cause problems due to ongoing infection and should be monitored closely by imaging. Publication bias and lack of long term follow up imply cautious interpretation of these findings

Crystal structure of racemic 2-[(ß-arabinopyranosyl)sulfanyl]-4,6-diphenylpyridine-3-carbonitrile

In the racemic title compound, C23H20N2O4S, the sulfur atom is attached equatorially to the sugar ring with unequal S—C bonds, viz.: S—Cs = 1.808 (2) and S—Cp = 1.770 (2) Å (s = sugar, p = pyrid­yl). The dihedral angles between the pyridine ring and its attached phenyl groups are 42.24 (8) and 6.37 (14)°. In the crystal, a system of classical O—H⋯O and O—H⋯(O,O) hydrogen bonds links the mol­ecules to form tube-like assemblies propagating parallel to the c-axis direction. Weak C—H⋯N inter­actions are also observed

Effect of First-Pass Reperfusion on Outcome After Endovascular Treatment for Ischemic Stroke

Background First-pass reperfusion (FPR) is associated with favorable outcome after endovascular treatment. It is unknown whether this effect is independent of patient characteristics and whether FPR has better outcomes compared with excellent reperfusion (Expanded Thrombolysis in Cerebral Infarction [eTICI] 2C-3) after multiple-passes reperfusion. We aimed to evaluate the association between FPR and outcome with adjustment for patient, imaging, and treatment characteristics to single out the contribution of FPR. Methods and Results FPR was defined as eTICI 2C-3 after 1 pass. Multivariable regression models were used to investigate characteristics associated with FPR and to investigate the effect of FPR on outcomes. We included 2686 patients of the MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) Registry. Factors associated with FPR were as follows: history of hyperlipidemia (adjusted odds ratio [OR], 1.05; 95% CI, 1.01-1.10), middle cerebral artery versus intracranial carotid artery occlusion (adjusted OR, 1.11; 95% CI, 1.06-1.16), and aspiration versus stent thrombectomy (adjusted OR, 1.07; 95% CI, 1.03-1.11). Interventionist experience increased the likelihood of FPR (adjusted OR, 1.03 per 50 patients previously treated; 95% CI, 1.01-1.06). Adjusted for patient, imaging, and treatment characteristics, FPR remained associated with a better 24-hour National Institutes of Health Stroke Scale (NIHSS) score (-37%; 95% CI, -43% to -31%) and a better modified Rankin Scale (mRS) score at 3 months (adjusted common OR, 2.16; 95% CI, 1.83-2.54) compared with no FPR (multiple-passes reperfusion+no excellent reperfusion), and compared with multiple-passes reperfusion alone (24-hour NIHSS score, (-23%; 95% CI, -31% to -14%), and mRS score (adjusted common OR, 1.45; 95% CI, 1.19-1.78)). Conclusions FPR compared with multiple-passes reperfusion is associated with favorable outcome, independently of patient, imaging, and treatment characteristics. Factors associated with FPR were the experience of the interventionist, history of hyperlipidemia, location of occluded artery, and use of an aspiration device compared with stent thrombectomy

Restoration of rostral cerebrospinal fluid flow to solve treatment failure caused by obstruction in long-term intrathecal baclofen administration

Objects: We describe five traumatic spinal cord injury (SCI) patients with an intrathecal baclofen administration (ITB) failure caused by a rostral CSF flow obstruction referred to our expert center between January 2014 and January 2019. We discuss the diagnostic workup, rostral CSF flow obstruction as the cause of the ITB failure and treatment. Methods: When we could not determine the cause of the ITB failure through the patient’s history, physical spasticity examination, pump readout, absence of fluid in the pump reservoir during aspiration, or plain radiography, we performed pump catheter access port (computed tomography [CT]) myelography. When CT myelography did not reveal the diagnosis, we used scintigraphy. In an obstruction, we aimed for CSF flow restoration. In three cases, we conducted a laminectomy with microsurgical adhesiolysis. In two of these patients, we could not achieve CSF flow restoration; thus, we placed an intradural catheter bypass. Recently, in three patients, we applied a less invasive technique of percutaneous fenestration of the obstruction. Results: In one case, we performed a successful catheter replacement. In another case using surgical adhesiolysis, spasticity control was complete. In two cases, we could obtain improvement with an additional intradural bypass, followed by a percutaneous fenestration of the obstruction, resulting in further improved CSF flow restoration. In one case, percutaneous fenestration was the first line of treatment. In all cases with percutaneous fenestration, we experienced spasticity control. Conclusion: Preliminary results showed that the restoration of rostral CSF flow might result in an effective ITB treatment in patients with an intrathecal obstruction

Impact of the lockdown on acute stroke treatments during the first surge of the COVID-19 outbreak in the Netherlands

INTRODUCTION: We investigated the impact of the Corona Virus Disease 2019 (COVID-19) pandemic and the resulting lockdown on reperfusion treatments and door-to-treatment times during the first surge in Dutch comprehensive stroke centers. Furthermore, we studied the association between COVID-19-status and treatment times. METHODS: We included all patients receiving reperfusion treatment in 17 Dutch stroke centers from May 11th, 2017, until May 11th, 2020. We collected baseline characteristics, National Institutes of Health Stroke Scale (NIHSS) at admission, onset-to-door time (ODT), door-to-needle time (DNT), door-to-groin time (DGT) and COVID-19-status at admission. Parameters during the lockdown (March 15th, 2020 until May 11th, 2020) were compared with those in the same period in 2019, and between groups stratified by COVID-19-status. We used nationwide data and extrapolated our findings to the increasing trend of EVT numbers since May 2017. RESULTS: A decline of 14% was seen in reperfusion treatments during lockdown, with a decline in both IVT and EVT delivery. DGT increased by 12 min (50 to 62 min, p-value of < 0.001). Furthermore, median NIHSS-scores were higher in COVID-19 - suspected or positive patients (7 to 11, p-value of 0.004), door-to-treatment times did not differ significantly when stratified for COVID-19-status. CONCLUSIONS: During the first surge of the COVID-19 pandemic, a decline in acute reperfusion treatments and a delay in DGT was seen, which indicates a target for attention. It also appeared that COVID-19-positive or -suspected patients had more severe neurologic symptoms, whereas their EVT-workflow was not affected. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12883-021-02539-4

Mechanistic Investigations into the Application of Sulfoxides in Carbohydrate Synthesis

The utility of sulfoxides in a diverse range of transformations in the field of carbohydrate chemistry has seen rapid growth since the first introduction of a sulfoxide as a glycosyl donor in 1989. Sulfoxides have since developed into more than just anomeric leaving groups, and today have multiple roles in glycosylation reactions. These include as activators for thioglycosides, hemiacetals, and glycals, and as precursors to glycosyl triflates, which are essential for stereoselective β- mannoside synthesis, and bicyclic sulfonium ions that facilitate the stereoselective synthesis of α-glycosides. In this review we highlight the mechanistic investigations undertaken in this area, often outlining strategies employed to differentiate between multiple proposed reaction pathways, and how the conclusions of these investigations have and continue to inform upon the development of more efficient transformations in sulfoxide based carbohydrate synthesis