A Concise Enantioselective Approach to Quassinoids.

A synthetic approach to quassinoids is described. The route to the tetracyclic core relies on an efficient and selective annulation between two unsaturated carbonyl components that is initiated by catalytic hydrogen atom transfer from an iron hydride to an alkene. Application of this strategy allows for enantioselective synthesis of quassin, which is prepared in 14 steps from commercially available starting material.

New Methods and Strategies in the Synthesis of Terpenoid Natural Products.

Indoloterpenoids of the paxilline type belong to a large family of secondary metabolites that exhibit unique molecular architectures and a diverse set of biological activities. More than 100 congeners identified to date share a common structural motif that contains an indole moiety fused to a rearranged diterpenoid fragment. The representative physiological and cellular effects attributed to this family of natural products include neurological and insecticidal activities, modulation of lipid balance, and inhibition of mitosis. The uniting polycyclic motif combined with the diversity of individual structural features of paxilline indoloterpenoids and the broad scope of their biological activities have fascinated organic chemists for the past four decades and have led to the development of numerous syntheses. In this Account, we describe our contributions to this field and how they in turn shape new directions that are developing in our laboratory.We begin with the discussion of our strategy for the synthesis of the shared indoloterpenoid core. To address stereochemical challenges encountered in earlier reports, we planned to leverage a suitably substituted cyclopentanone in a polycyclization to form the desired trans-decalin motif. This polycyclization relied on a radical-polar crossover cascade initiated by hydrogen atom transfer. The original process exhibited poor diastereoselectivity, but we discovered an efficient solution to this problem that took advantage of intramolecular tethering effects, culminating in short synthesis of emindole SB. During these studies, we also identified indium-mediated alkenylation of silyl enol ethers with alkynes as a suitable method for the synthesis of highly substituted ß,γ-unsaturated ketones that was critical to achieving brevity of our route. We subsequently developed a catalytic version of this transformation that allowed for a formal bimolecular ene reaction that exhibited unusual and potentially useful selectivity in construction of quaternary centers.To test the scope and limitations of our approach to paxilline indoloterpenoids and identify potential improvements, we developed a synthesis of the more complex congener nodulisporic acid C. The convergent assembly of this natural product was enabled by identification of new elements of stereocontrol in the radical-polar crossover polycyclization en route to the polycyclic terpenoid motif and development of a highly diastereoselective enyne cycloisomerization to access the indenopyran motif and a ketone arylation protocol to unite the two complex fragments.In subsequent studies, we expanded the radical-polar crossover cascade underlying our approach to paxilline indoloterpenoids to a bimolecular setting, which allowed for annulation of two unsaturated carbonyl components to produce functionalized cyclohexanes. This transformation is particularly well suited for installation of fully substituted carbons and can be complementary to the venerable Diels-Alder reaction. The utility of the new annulation was tested in the synthesis of forskolin, allowing for rapid construction of the complex polycyclic motif in this densely functionalized labdane diterpenoid.Over the past five years, our initial forays into the synthesis of paxilline indoloterpenoids have grown into a program that incorporates development of new synthetic methods and pursues artificial assembly of terpenoid natural products from several different families. We are encouraged by the increasing diversity of structural motifs made accessible by application of this chemistry and continue to discover new aspects of the underlying reactivity.

A Radical-Polar Crossover Annulation To Access Terpenoid Motifs.

A new catalytic radical-polar crossover annulation between two unsaturated carbonyl compounds is described. The annulation proceeds under exceptionally mild conditions and provides direct and expedient access to complex terpenoid motifs. Application of this chemistry allows for synthesis of forskolin, a densely functionalized terpenoid, in 14 steps from commercially available material.

Pulmonary artery dissection in eight dogs with patent ductus arteriosus.

OBJECTIVES: To describe a series of dogs with pulmonary artery dissection and patent ductus arteriosus (PDA). ANIMALS: Eight dogs. METHODS: Retrospective case series. RESULTS: Pulmonary artery dissection was diagnosed in 8 dogs, 3 were Weimaraners. Four dogs presented in left-sided congestive heart failure, 4 presented for murmur evaluation and without clinical signs, and 1 presented in right-sided congestive heart failure. In 7 dogs the dissection was first documented concurrent with a diagnosis of uncorrected PDA. In the other dog, with pulmonary valve stenosis and PDA, the dissection was observed on autopsy examination 17 months after balloon pulmonary valvuloplasty and ductal closure. Median age at presentation for the 7 dogs with antemortem diagnosis of pulmonary artery dissection was 3.5 years (range, 1.5-4 years). Three dogs had the PDA surgically ligated, 2 dogs did not undergo PDA closure, 1 dog failed transcatheter occlusion of the PDA with subsequent surgical ligation, 1 dog underwent successful transcatheter device occlusion of the PDA, and 1 dog had the PDA closed by transcatheter coil delivery 17 months prior to the diagnosis of pulmonary artery dissection. The 2 dogs that did not have the PDA closed died 1 and 3 years after diagnosis due to heart failure. CONCLUSIONS: Pulmonary artery dissection is a potential complication of PDA in dogs, the Weimaraner breed may be at increased risk, presentation is often in mature dogs, and closure of the PDA can be performed and appears to improve outcome.

Two-dimensionally-guided M-mode and pulsed wave Doppler echocardiographic evaluation of the ventricles of apparently healthy cats.

OBJECTIVE: To determine two-dimensionally-guided (2D-guided) M-mode and pulsed-wave (PW) Doppler echocardiographic reference intervals range of healthy non-sedated cats. ANIMALS: Fifty-three healthy, unsedated domestic cats. MATERIALS AND METHODS: Cats were interrogated via standard imaging planes with 2D-guided PW Doppler, using 5.0 and 7.5 MHz duplex imaging transducers. Left ventricular (LV) M-mode measurements and intracardiac PW Doppler data were acquired using ACVIM guidelines for echocardiography. Doppler variables of the same region, measured from different views, were compared for agreement where appropriate. Descriptive statistics were provided for all measured variables. Statistical comparisons of selected M-mode and PW Doppler echocardiographic variables and correlations with weight or age were made, with significance set at P < 0.01. RESULTS: Most cats (42/51) had diastolic LV septal and posterior wall diastolic dimensions <4.5 mm (maximum = 5.7 mm). Only septal diastolic wall dimension correlated weakly with body weight (ρ = 0.36). Median peak transvalvular velocities (m/s) were: aorta 1.04 (range: 0.77-1.40); LV inflow 0.60 (range: 0.43-0.95) (E wave), 0.47 (range: 0.32-0.76) (A wave), RV inflow 0.56 (range: 0.37-0.85), pulmonic valve (right) 0.96 (range: 0.65-1.21). For mitral valve inflow, the E and A waves were usually separately measurable at heart rates ≈ <180/min, merging into a single diastolic wave (EA) at heart rates ≈ >190/min. Peak E wave velocity correlated with heart rate. No variables correlated with age. CONCLUSIONS: Our study provides comprehensive 2D-guided echocardiographic M-mode and PW Doppler reference data for apparently healthy cats.

Congenital supravalvular mitral stenosis in 14 cats.

OBJECTIVES: To describe the clinical features of congenital supravalvular mitral stenosis (SVMS) in cats. BACKGROUND: Supravalvular mitral stenosis is an uncommon congenital cardiac defect that has not been previously reported in a series of cats. ANIMALS: 14 cats with SVMS. METHODS: Medical records, relevant diagnostic studies and preserved pathology specimens were reviewed. RESULTS: Cats were presented over a wide age range (5 months-10 years; median 3 years); males (n = 9) and the Siamese breed were over-represented. Presenting complaints included respiratory distress (n = 6), hindlimb paralysis due to aortic thromboembolism (n = 5) and asymptomatic heart murmur (n = 3). Echocardiographic examination often identified pulmonary hypertension (PHT) (n = 7) and concurrent cardiac abnormalities (n = 7), especially partial atrioventricular septal defect (PAVSD) (n = 4). Status 12 months following diagnosis was known for 9 cats; 8 of these had died or were euthanized. CONCLUSIONS: Cats with SVMS are usually presented as young adults for respiratory signs attributable to congestive heart failure, aortic thromboembolism or incidental murmur identification. Congestive heart failure, PHT and concurrent congenital cardiac abnormalities (specifically PAVSD) are common. Long-term prognosis for symptomatic cats is poor.

Coil embolization of patent ductus arteriosus via the carotid artery in seven dogs.

This study was designed to evaluate the feasibility and limitations of transcatheter embolization coil occlusion of patent ductus arteriosus in dogs using a carotid artery approach. Seven dogs examined at the University of California, Davis Veterinary Medical Teaching Hospital in 2002-2003 for evaluation of heart disease had congenital patent ductus arteriosus diagnosed by characteristic physical, electrocardiographic, radiographic, and anatomic and Doppler echocardiographic findings. Dogs were anesthetized for transesophageal echocardiography and transcatheter coil embolization of the ductus via the right external carotid artery. Coil embolization was achieved in all seven cases, using one to four detachable embolization coils. There were no major complications. Minor complications occurred in two dogs (additional coils placed using a femoral arterial approach and coil embolization of a left femoral artery branch). One dog was examined only 24 h post-operatively and had no murmur and trivial residual ductal flow by Doppler echocardiography. The other 6 dogs were clinically healthy when examined up to three years post-intervention. One dog had a very soft continuous murmur and mild residual ductal flow; the other five had no audible continuous murmur, with only one dog having trivial residual ductal flow identified by Doppler echocardiography. Although technically challenging, coil embolization via the carotid artery is a viable alternative approach for transcatheter closure of patent ductus arteriosus in some dogs.

Infective endocarditis in a dog and the phylogenetic relationship of the associated "Bartonella rochalimae" strain with isolates from dogs, gray foxes, and a human.

The first case of canine endocarditis caused by "Bartonella rochalimae" is reported. By PCR-restriction fragment length polymorphism, sequence, and phylogenetic analyses, Bartonella isolates from a dog with endocarditis, 22 gray foxes, and three dogs, described as B. clarridgeiae like, were confirmed to belong to the new species "B. rochalimae," suggesting canids as the natural reservoir.

Congenital mitral stenosis, subvalvular aortic stenosis, and congestive heart failure in a duck.

A 2.6-year-old duck was evaluated for respiratory difficulty. On the basis of physical, radiographic and echocardiographic findings, a diagnosis of congestive heart failure secondary to congenital mitral stenosis and subvalvular aortic stenosis was made. The duck did not respond well to medical therapy and was euthanized. The diagnosis was confirmed at necropsy.

Applications, complications, and outcomes of transvenous pacemaker implantation in 105 dogs (1997-2002).

We reviewed the indications for age and breeds of dogs who received transvenous endocardial artificial pacemaker (AP) implantation (n = 105) and complications and survival thereafter at a single institution over a 6-year period. A third-degree atrioventricular (AV) block (59%) and sick sinus syndrome (SSS; 27%) were the most common indications, along with a high-grade second-degree AV block (9%) and atrial standstill (5%). The most common breeds identified were Labrador Retriever (n = 16; 11 with a third-degree AV block), American Cocker Spaniel (n = 14; 10 with SSS), and Miniature Schnauzer (n = 13; all with SSS). Common presenting complaints were syncope (n = 66) and exercise intolerance or lethargy (n = 25). Half of the dogs (n = 52) had a history of acute onset of clinical signs (<2 weeks). Mean survival time for the 60 dogs who died during the study period was 2.2 years (range, 0.1-5.8 years). Major complications occurred in 13% of dogs and included lead displacement (n = 7), sensing problems that led to syncope (n = 3), infection at the pacemaker site (n = 1), bleeding (n = 1), and ventricular fibrillation during implantation (n = 1; successfully defibrillated). Minor complications occurred in 11 dogs (11%). The success rate of transvenous AP implantation was comparatively high (all dogs survived the first 48 hours), and the complication rate was comparatively low when compared with a previous multicenter study, most likely because of how commonly the procedure was performed and supervisory experience.

Outer chain N-glycans are required for cell wall integrity and virulence of Candida albicans.

The outer layer of the Candida albicans cell wall is enriched in highly glycosylated mannoproteins that are the immediate point of contact with the host and strongly influence the host-fungal interaction. N-Glycans are the major form of mannoprotein modification and consist of a core structure, common to all eukaryotes, that is further elaborated in the Golgi to form the highly branched outer chain that is characteristic of fungi. In yeasts, outer chain branching is initiated by the action of the alpha1,6-mannosyltransferase Och1p; therefore, we disrupted the C. albicans OCH1 homolog to determine the importance of outer chain N-glycans on the host-fungal interaction. Loss of CaOCH1 resulted in a temperature-sensitive growth defect and cellular aggregation. Outer chain elongation of N-glycans was absent in the null mutant, demonstrated by the lack of the alpha1,6-linked polymannose backbone and the underglycosylation of N-acetylglucosaminidase. A null mutant lacking OCH1 was hypersensitive to a range of cell wall perturbing agents and had a constitutively activated cell wall integrity pathway. These mutants had near normal growth rates in vitro but were attenuated in virulence in a murine model of systemic infection. However, tissue burdens for the Caoch1delta null mutant were similar to control strains with normal N-glycosylation, suggesting the host-fungal interaction was altered such that high burdens were tolerated. This demonstrates the importance of N-glycan outer chain epitopes to the host-fungal interaction and virulence.

Echocardiographic diagnosis of congenital membranous ventricular septal aneurysm in the dog and cat.

Membranous ventricular septal aneurysm was diagnosed by echocardiography in 17 dogs and three cats. The aneurysm appeared as a thin membrane protruding into the right ventricle from the margins of a congenital ventricular septal defect (VSD). The aneurysm was intact in nine dogs and two cats and perforated by a small VSD in eight dogs and one cat. Other congenital heart defects were present in seven dogs. In all animals, the aneurysm was an incidental finding observed during echocardiographic examination, and it did not appear to directly cause any cardiac dysfunction.

Pericarditis and pleuritis caused by Corynebacterium pseudotuberculosis in a horse.

A 13-year-old Oldenburg mare was evaluated for lethargy and signs of mild colic. Pericardial tamponade caused by fibrinoeffusive pericarditis was diagnosed. Cytologic and biochemical evaluation of pericardial fluid was consistent with a septic effusion. Corynebacterium pseudotuberculosis, the cause of pigeon fever, was identified by bacteriologic culture of pericardial fluid. Drainage and lavage of the pericardial sac, local (intrapericardial) and systemic antimicrobial treatment, and subsequent corticosteroid treatment resulted in a successful outcome in this horse. To the authors' knowledge, this is the first report of pericarditis associated with C pseudotuberculosis in a horse.

A prospective study of canine infective endocarditis in northern California (1999-2001): emergence of Bartonella as a prevalent etiologic agent.

A prospective study was performed (June 1999 to May 2001) to determine the incidence of infective endocarditis (IE) due to Bartonella in dogs in northern California and to compare these patients with other dogs with IE. IE was diagnosed antemortem based on clinical signs and echocardiography in 18 dogs. The etiologic agent was Bartonella sp. in 5 dogs (28%) and was diagnosed by high seroreactivity to Bartonella (titer > 1:512; range, 1:1,024-1:4,096); and confirmed postmortem by positive polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) from the infected valve and partial DNA sequencing of the citrate synthase gene (glt A). Conventional bacteria were causative agents in 7 dogs (39%). An etiologic agent was not identified in 6 dogs (33%). Bartonella vinsonii berkhoffii (n = 3), B clarridgeiae (n = 1), and a B clarridgeiae-like organism (n = 1) were identified. Blood culture was positive only for the IE case due to B clarridgeiae. All dogs with IE due to Bartonella were also seroreactive to Anaplasma phagocytophilum. All dogs with IE due to Bartonella had lesions only on the aortic valve. Of the cases of IE not due to Bartonella, 31% involved the aortic valve, 61% the mitral valve, and 8% both valves. Dogs with mitral valve IE lived longer than all dogs with aortic valve IE (P = .004) and dogs with IE of the aortic valve due to Bartonella (P = .002). In conclusion, Bartonella is a common cause of IE in dogs of northern California. A high Bartonella serologic titer (> 1:512) is useful antemortem to diagnose aortic valve IE due to Bartonella.

Dynamic right ventricular outflow obstruction: a new cause of systolic murmurs in cats.

We have identified and characterized a new cause of variable parasternal systolic murmurs in cats. Color Doppler echocardiography of 51 cats presented for evaluation of a cardiac murmur demonstrated a localized, turbulent systolic jet located within the right ventricular (RV) outflow region, originating just cranial to the tricuspid valve. Spectral Doppler tracings of the turbulent jets showed abnormally high peak velocity, late systolic flow acceleration, and marked variability with heart rate, typical of dynamic stenosis. Frame-by-frame examination of 2-dimensional (2D) echocardiographic images after color Doppler subtraction revealed systolic apposition of the RV free wall with the interventricular septum at the origin of the turbulent jets. Therefore, we termed this turbulent flow pattern "dynamic right ventricular obstruction" (DRVO). Most cats with DRVO were >4 years old (45 of 51, 88%) and initially presented with concurrent noncardiac disease (73%). Noncardiac diseases associated with DRVO in older cats included high cardiac output states (hyperthyroidism, anemia, and inflammatory disease) and chronic renal failure with and without systemic hypertension. Of the 45 cats >4 years old, 4 (9%) had no evidence of any other cardiac or noncardiac disease. In contrast, 5 of 6 cats (83%) <4 years old had concurrent cardiac disease. No breed predisposition was identified. Follow-up examination of 10 cats demonstrated no change in the disorder in 8 cats but revealed the disappearance of the murmur and abnormal RV Doppler flow signal in 2 cats after renal transplantation. We propose that DRVO is a physiologic cause of systolic murmurs in cats attributable to RV systolic narrowing.

Two-dimensional and M-mode echocardiographic predictors of disease severity in dogs with congenital subaortic stenosis.

Echocardiographic studies from 50 dogs with congenital subaortic stenosis were examined. The degree of concentric, left-ventricular hypertrophy as assessed by M-mode measurement demonstrated a positive relationship (P<0.05) to disease severity. However, the clinical utility of these measures is hindered by a large amount of individual variation (r2=0.243 to 0.473). Two-dimensional ultrasound was used to compare the cross-sectional area of the left-ventricular outflow tract to the cross-sectional area of the aortic root. The ratio of these two areas demonstrated a strong inverse relationship (P=0.001; r2=0.778) with disease severity. This ratio provides a method of estimating severity of disease by two-dimensional echocardiography.