Data-Driven Multi-Objective Optimization Tactics for Catalytic Asymmetric Reactions Using Bisphosphine Ligands

Optimization of the catalyst structure to simultaneously improve multiple reaction objectives (e.g., yield, enantioselectivity, and regioselectivity) remains a formidable challenge. Herein, we describe a machine learning workflow for the multi-objective optimization of catalytic reactions that employ chiral bisphosphine ligands. This was demonstrated through the optimization of two sequential reactions required in the asymmetric synthesis of an active pharmaceutical ingredient. To accomplish this, a density functional theory-derived database of >550 bisphosphine ligands was constructed, and a designer chemical space mapping technique was established. The protocol used classification methods to identify active catalysts, followed by linear regression to model reaction selectivity. This led to the prediction and validation of significantly improved ligands for all reaction outputs, suggesting a general strategy that can be readily implemented for reaction optimizations where performance is controlled by bisphosphine ligands.

Asymmetric Hydrogenation of Unfunctionalized Tetrasubstituted Acyclic Olefins

Asymmetric hydrogenation has evolved as one of the most powerful tools to construct stereocenters. However, the asymmetric hydrogenation of unfunctionalized tetrasubstituted acyclic olefins remains the pinnacle of asymmetric synthesis and an unsolved challenge. We report herein the discovery of an iridium catalyst for the first, generally applicable, highly enantio- and diastereoselective hydrogenation of such olefins and the mechanistic insights of the reaction. The power of this chemistry is demonstrated by the successful hydrogenation of a wide variety of electronically and sterically diverse olefins in excellent yield and high enantio- and diastereoselectivity.

Phosphoramidates as Steering Elements for Highly Selective Access to Complementary Imidazo[1,2-a]pyrimidine Isomers

We report that selective N-phosphorylation of aminoimidazoles results in a key steering element that controls isomeric selectivity in the condensation of β-ethoxy acrylamides and aminoimidazoles to furnish imidazo[1,2-a]pyrimidines. We identified conditions that provide highly selective (99:1) phosphorylation at the endo- or exocyclic nitrogen. Either the 2-amino or 4-amino isomer of the (benzo)imidazo[1,2-a]pyrimidine products could be isolated in 64-95% yield. Mass spectrometric analysis and computational studies give insight into the mechanism of this exceptionally selective transformation.

Case for Lithium Tetramethylpiperidide-Mediated Ortholithiations: Reactivity and Mechanisms

Rate and mechanistic studies of ortholithiations by lithium 2,2,6,6-tetramethylpiperidide focus on four arenes: 1,4-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,3-dimethoxybenzene, and 4,4-dimethyl-2-phenyl-2-oxazoline. Metalations occur via substrate-dependent combinations of monosolvated monomer, disolvated monomer, and tetrasolvated dimer (triple ions). Density functional theory computational studies augment the experimental data. We discuss the challenges presented by shifting dimer-monomer proportions in determining the observable reaction orders and our mathematical treatment of such shifting in reactant structure.

Lithium Hexamethyldisilazide-Mediated Enolization of Highly Substituted Aryl Ketones: Structural and Mechanistic Basis of the E/Z Selectivities

Enolizations of highly substituted acyclic ketones used in the syntheses of tetrasubstituted olefin-based anticancer agents are described. Lithium hexamethyldisilazide (LiHMDS)-mediated enolizations are moderately Z-selective in neat tetrahydrofuran (THF) and E-selective in 2.0 M THF/hexane. The results of NMR spectroscopy show the resulting enolates to be statistically distributed ensembles of E,E-, E,Z-, and Z,Z-enolate dimers with subunits that reflect the selectivities. The results of rate studies trace the preference for E and Z isomers to tetrasolvated- and pentasolvated-monomer-based transition structures, respectively. Enolization using LiHMDS in N,N-dimethylethylamine or triethylamine in toluene affords a 65:1 mixture of LiHMDS-lithium enolate mixed dimers containing E and Z isomers, respectively. Spectroscopic studies show that condition-dependent complexation of ketone to LiHMDS occurs in trialkylamine/toluene. Rate data attribute the high selectivity exclusively to monosolvated-dimer-based transition structures.

Highly Stereoselective Synthesis of Tetrasubstituted Acyclic All-Carbon Olefins via Enol Tosylation and Suzuki-Miyaura Coupling

A highly stereocontrolled synthesis of tetrasubstituted acyclic all-carbon olefins has been developed via a stereoselective enolization and tosylate formation, followed by a palladium-catalyzed Suzuki-Miyaura cross-coupling of the tosylates and pinacol boronic esters in the presence of a Pd(OAc)2/RuPhos catalytic system. Both the enol tosylation and Suzuki-Miyaura coupling reactions tolerate an array of electronically and sterically diverse substituents and generate high yield and stereoselectivity of the olefin products. Judicious choice of substrate and coupling partner provides access to either the E- or Z-olefin with excellent yield and stereochemical fidelity. Olefin isomerization was observed during the Suzuki-Miyaura coupling. However, under the optimized cross-coupling reaction conditions, the isomerization was suppressed to <5% in most cases. Mechanistic probes indicate that the olefin isomerization occurs via an intermediate, possibly a zwitterionic palladium carbenoid species.

Lithium Enolates in the Enantioselective Construction of Tetrasubstituted Carbon Centers with Chiral Lithium Amides as Noncovalent Stereodirecting Auxiliaries

Lithium enolates derived from carboxylic acids are ubiquitous intermediates in organic synthesis. Asymmetric transformations with these intermediates, a central goal of organic synthesis, are typically carried out with covalently attached chiral auxiliaries. An alternative approach is to utilize chiral reagents that form discrete, well-defined aggregates with lithium enolates, providing a chiral environment conducive of asymmetric bond formation. These reagents effectively act as noncovalent, or traceless, chiral auxiliaries. Lithium amides are an obvious choice for such reagents as they are known to form mixed aggregates with lithium enolates. We demonstrate here that mixed aggregates can effect highly enantioselective transformations of lithium enolates in several classes of reactions, most notably in transformations forming tetrasubstituted and quaternary carbon centers. Easy recovery of the chiral reagent by aqueous extraction is another practical advantage of this one-step protocol. Crystallographic, spectroscopic, and computational studies of the central reactive aggregate, which provide insight into the origins of selectivity, are also reported.

Mixed Aggregates of the Dilithiated Koga Tetraamine: NMR Spectroscopic and Computational Studies

A combination of (1) H, (6) Li, (13) C, and (15) N NMR spectroscopies and density functional theory computations explores the formation of mixed aggregates by a dilithium salt of a C2 -symmetric chiral tetraamine (Koga's base). Lithium halides, acetylides, alkoxides, and monoalkylamides form isostructural trilithiated mixed aggregates with few exceptions. (6) Li-(13) C and (6) Li-(15) N couplings reveal heretofore undetected transannular contacts (laddering) with lithium acetylides and lithium monoalkylamides. Marked temperature-dependent (15) N chemical shifts seem to be associated with this laddering. Computational studies shed light on the general structures of the aggregates, their penchant for laddering, and the stereochemical consequences of aggregation.

Self-reported falls and fall-related injuries among persons aged>or=65 years--United States, 2006

PROBLEM

In 2005, 15,802 persons aged>or=65 years died from fall injuries. How many older adults seek outpatient treatment for minor or moderate fall injuries is unknown.

METHOD

To estimate the percentage of older adults who fell during the preceding three months, the Centers for Disease Control and Prevention (CDC) analyzed data from two questions about falls included in the 2006 Behavioral Risk Factor Surveillance System (BRFSS) survey.

RESULTS

Approximately 5.8 million (15.9%) persons aged>or=65 years reported falling at least once during the preceding three months, and 1.8 million (31.3%) of those who fell sustained an injury that resulted in a doctor visit or restricted activity for at least one day.

DISCUSSION

This report presents the first national estimates of the number and proportion of persons reporting fall-related injuries associated with either doctor visits or restricted activity.

SUMMARY

The prevalence of falls reinforces the need for broader use of scientifically proven fall-prevention interventions.

IMPACT ON INDUSTRY

Falls and fall-related injuries represent an enormous burden to individuals, society, and to our health care system. Because the U.S. population is aging, this problem will increase unless we take preventive action by broadly implementing evidence-based fall prevention programs. Such programs could appreciably decrease the incidence and health care costs of fall injuries, as well as greatly improve the quality of life for older adults.

HIV-related behaviors and perceptions among adults in 25 states: 1997 Behavioral Risk Factor Surveillance System

OBJECTIVES

To assess the level of HIV-related risk behavior among the general US adult population, we analyzed data from the first sexual behavior questions available for states to use with the Behavioral Risk Factor Surveillance System.

METHODS

The Behavioral Risk Factor Surveillance System is a state-specific, population-based, random telephone survey. In 1997, 25 states collected sexual behavior data. Annual prevalence estimates for selected behaviors were calculated and examined by sociodemographic characteristics. The correlation between actual and perceived HIV risk also was determined.

RESULTS

Most (77.1%) of the respondents reported just 1 sexual partner in the past year; 26.0% reported using a condom at last intercourse. Males, persons who were younger, and Blacks were more likely to report 2 or more partners but also more likely to report using a condom at last intercourse. Only 4.1% of the respondents reported a risk factor for HIV infection; 7.7% reported that they were at medium or high risk for HIV. Actual and perceived HIV risk were positively associated.

CONCLUSIONS

Most US adults do not engage in HIV-related risk behavior; those that do are more likely to report protective behavior.

Sequencing of the Francisella tularensis strain Schu 4 genome reveals the shikimate and purine metabolic pathways, targets for the construction of a rationally attenuated auxotrophic vaccine

Francisella tularensis is the etiological agent of tularemia, a serious disease in several Northern hemisphere countries. The organism has fastidious growth requirements and is very poorly understood at the genetic and molecular levels. Given the lack of data on this organism, we undertook the sample sequencing of its genome. A random library of DNA fragments from a highly virulent strain (Schu 4) of F. tularensis was constructed and the nucleotide sequences of 13,904 cloned fragments were determined and assembled into 353 contigs. A total of 1.83 Mb of nucleotide sequence was obtained that had a G+C content of 33.2%. Genes located on plasmids pOM1 and pNFL10, which had been previously isolated from low virulence strains of F. tularensis, were absent but all of the other known F. tularensis genes were represented in the assembled data. F. tularensis Schu4 was able to grow in the absence of aromatic amino acids and orthologues of genes which could encode enzymes in the shikimate pathway in other bacteria were identified in the assembled data. Genes that could encode all of the enzymes in the purine biosynthetic and most of the en- zymes in the purine salvage pathways were also identified. This data will be used to develop defined rationally attenuated mutants of F. tularensis, which could be used as replacements for the existing genetically undefined live vaccine strain.

Reliability and validity of measures from the Behavioral Risk Factor Surveillance System (BRFSS)

OBJECTIVES

To assess the reliability and validity of measures on the BRFSS, to assist users in evaluating the quality of BRFSS data, and to identify areas for further research.

METHODS

Review and summary of reliability and validity studies of measures on the BRFSS and studies of measures that were the same or similar to those on the BRFSS from other surveys.

RESULTS

Measures determined to be of high reliability and high validity were current smoker, blood pressure screening, height, weight, and BMI, and several demographic characteristics. Measures of both moderate reliability and validity included when last mammography was received, clinical breast exam, sedentary lifestyle, intense leisure-time physical activity, and fruit and vegetable consumption. Few measures were of low validity and only one measure was determined to be of low reliability. Several other measures were of high or moderate reliability or validity, but not both. The reliability or validity could not be determined for some measures, primarily due to lack of research.

CONCLUSIONS

Most questions on the core BRFSS instrument were at least moderately reliable and valid, and many were highly reliable and valid. Additional research is needed for some measures.

Acupressure for nausea: results of a pilot study

PURPOSE/OBJECTIVES

To compare differences in nausea experience and intensity in women undergoing chemotherapy for breast cancer between those receiving usual care plus acupressure training and treatment and those receiving only usual care.

DESIGN

Single-cycle, randomized clinical trial.

SETTING

Outpatient oncology clinic in a major teaching medical center and a private outpatient oncology practice.

SAMPLE

Seventeen women participated in the study. The typical participant was 49.5 years old (SD = 6.0), Caucasian (59%), not married/partnered (76%), on disability (53%), born a U.S. citizen (76%), and heterosexual (88%); lived alone (59%); had at least graduated from high school (100%); and had an annual personal income of $50,000 or greater (65%).

METHODS

The intervention included finger acupressure bilaterally at P6 and ST36, acupressure points located on the forearm and by the knee. Baseline and poststudy questionnaires plus a daily log were used to collect data.

MAIN RESEARCH VARIABLES

Nausea experience measured by the Rhodes inventory of Nausea, Vomiting, and Retching and nausea intensity.

FINDINGS

Significant differences existed between the two groups in regard to nausea experience (p < 0.01) and nausea intensity (p < 0.04) during the first 10 days of the chemotherapy cycle, with the acupressure group reporting less intensity and experience of nausea.

CONCLUSIONS

Finger acupressure may decrease nausea among women undergoing chemotherapy for breast cancer.

IMPLICATIONS FOR NURSING PRACTICE

This study must be replicated prior to advising patients about the efficacy of acupressure for the treatment of nausea.

HIV testing behaviors and attitudes regarding HIV/AIDS of adults aged 50-64

This article explores knowledge, attitudes, and behaviors regarding HIV/AIDS for persons aged 50-64 by using data from the 1996 Behavioral Risk Factor Surveillance System. It examines what percentage have been tested for HIV, where and why they have been tested, knowledge about condom effectiveness, and self-perceived risk. The purpose is twofold: First, it presents an epidemiologic analysis of HIV/AIDS-related attitudes and behaviors of adults aged 50-64; second, it explores whether theoretical models used on other groups fit well with this age group. The authors conclude that the conceptual model is less robust for this group and there is a substantial need for health promotion efforts directed at older adults.

Corneal topography after excimer laser photorefractive keratectomy for myopia

BACKGROUND

This study was performed to assess and correlate the changes in central corneal power with the changes in manifest refraction after myopic photorefractive keratectomy (PRK) and to measure ablation zone centration.

METHODS

Fourteen patients had computerized videokeratography and manifest refraction performed preoperatively, and than 1, 2, 3, 4, 6, and 12 months after photorefractive keratectomy.

RESULTS

There was a significant association (r = -0.9; p < 0.0001) between changes in manifest refraction and changes in central corneal power at the 12-month postoperative examination; however, a mean difference of 1.1 D was seen between the two readings. The mean decentration of the ablation zone was 0.47 +/- 0.26 mm (range, 0.08 to 1.05 mm: 0 to 0.49 mm, six patients; 0.50 to 0.99 mm, seven patients; and 1.00 to 1.50 mm, one patient).

CONCLUSIONS

Corneal power-as measured by videokeratography-is not an accurate predictor of manifest refraction, although the two parameters did demonstrate good correlation. Centration of ablations was comparable to previous studies.

Central and peripheral endothelial cell changes after excimer laser photorefractive keratectomy for myopia

OBJECTIVE

To investigate changes in the human corneal endothelium after photorefractive keratectomy for treatment of myopia.

DESIGN

Specular microscopy of the central, paracentral, and peripheral zones of the corneas of 14 patients (12 of whom were previous contact lens wearers) was performed preoperatively and at 1, 2, 3, 6, and 12 months after photorefractive keratectomy. The corneal endothelial cell density, coefficient of variation (CV) of the endothelial cell area, and percentage of hexagonal cells were assessed at each examination.

RESULTS

The central endothelial cell density was increased by 7% during the first 3 postoperative months (P < .05). In contrast, the peripheral cell density declined steadily by 6.9% during the first year (P < .01). The CV of the cell area was decreased in all 3 zones, whereas the percentage of hexagonal cells was increased in the central and paracentral zones (P < .05).

CONCLUSIONS

We observed statistically significant changes in the central and peripheral endothelial cell densities and morphological features that could have resulted from photorefractive keratectomy; however, these changes also may have been explained by the discontinuation of contact lens wear. If such changes are contact lens-related, they could mask the effects of laser-induced damage to the central zone of the endothelium.