Lewis Base Catalyzed, Sulfenium Ion Initiated Enantioselective, Spiroketalization Cascade

Copper(I)-Catalyzed Asymmetric α-Selenenylation of 2-Acylimidazoles

A general method for the catalytic asymmetric α-selenenylation of simple carbonyl compounds is lacking. Herein, a copper(I)-catalyzed enantioselective α-selenenylation of 2-acylimidazoles with electrophilic selenosulfonates is uncovered. The reaction enjoys the advantages of mild conditions, easy reaction protocol, and broad substrate scopes on both 2-acylimidazoles and selenosulfonates. Mechanistic studies reveal a pincer Cu(I)-(S,S)-Ph-BOPA complex as the active catalyst. Some traditional electrophilic selenenylation reagents, such as PhSeCl, PhSeSePh, and 2-(phenylselanyl)isoindoline-1,3-dione lead to inferior results in terms of both yield and enantioselectivity, highlighting the superiority of selenosulfonates. Finally, several transformations based on both the 2-acylimidazole group and the selenoether group are successfully carried out, demonstrating the synthetic utilities of the present methodology.

Fluoroalcohols for chemical modification of biomolecules

While their broad utility in various chemistry fields were well recognized for decades, fluoroalcohols have recently emerged as a unique solvent system for bioconjugation development. This review describes examples and roles of fluoroalcohols such as trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) for chemical modification of biomolecules such as polypeptides, nucleic acids, and saccharides. Many chemical modification processes were facilitated by notable functions of those fluoroalcohols such as a proton shuttle, reversible adduct formation with reactive species, and compatibility with electrochemistry/photochemistry. The usefulness of the fluoroalcohol solvents can be even promoted by its combination with a different solvent system for reaction enhancement and protein stabilization. The collection of the various chemical transformations in this review is an indication of the rapid growth of the solvent-assisted bioconjugation field.

School performances in children with cataract: results from a population-based cohort study

OBJECTIVES

Childhood cataract is a chronic condition that may interfere with the child's learning capacities. We aimed to investigate whether childhood cataract influences academic development by comparing school performance in reading and mathematics in children with cataract to a matched control group.

DESIGN

Nationwide registry-based cohort study.

SETTINGS

Two surgical centres that perform all treatments for childhood cataract in Denmark.

PARTICIPANTS

Children born between 2000 and 2009 diagnosed with cataract before 10 years of age (n=275) and an age-matched and sex-matched control group (n=2473).

MAIN OUTCOME MEASURES

School performance was assessed as test scores in national tests performed at regular intervals from grade 2 to grade 8 in reading and mathematics. Analyses were corrected for birth origin, child somatic and mental disorder and parental socioeconomic status and mental disorders.

RESULTS

Of 275 children, 85 (30.9%) were operated for bilateral cataract, 79 (28.7%) unilateral cataract and 111 (40,4%) were not operated. We found that children with cataract have lower participation rate in the tests (62.5%) compared with the control cohort (77.2%) (p value=0.0001). After adjusting the pooled analyses for birth origin, somatic and mental disease in the child and parental socioeconomic status and mental disorders, we found that the children with cataract scored significantly lower in mathematics compared with those without cataract (mean difference=-4.78, 95% CI: -8.18 to -1.38, p value=0.006), whereas no difference was found regarding scores in reading (p=0.576). The lower score in mathematics was driven by children who had been operated for bilateral cataract (p-value=0.004).

CONCLUSION

Children with cataract without somatic or neurodevelopmental comorbidities or psychosocial adversities seem to do well in school, whereas children operated for bilateral cataract have higher frequencies of difficulties in mathematical tasks.

Enantioselective Synthesis of Spiroketals and Spiroaminals via Gold and Iridium Sequential Catalysis

The enantioselective cascade reaction between racemic 2-(1-hydroxyallyl)phenols and alkynols/alkynamides was realized by using a gold and iridium sequential catalytic system. In this procedure, the in situ generated exocyclic vinyl ethers or enamides undergo the asymmetric allylation/spiroketalization with π-ally-Ir amphiphilic species, which provides an efficient and straightforward access to spiroketals and spiroaminals with excellent enantioselectivities. Moreover, racemic 2-(1-hydroxyallyl)anilines were also suitable in this reaction along with a kinetic resolution process, affording enantioenriched spiroaminals and 2-(1-hydroxyallyl)anilines in good yields. The synthetic utility of this method has been demonstrated by efficient enantioselective synthesis of the analogue of Paecilospirone.

A Mechanistically Inspired Halenium Ion Initiated Spiroketalization: Entry to Mono- and Dibromospiroketals

Employing halenium affinity (HalA) as a guiding tool, the weak nucleophilic character of alkyl ketones was modulated by the templating effect of a tethered 2-tetrahydropyranyl(THP)-protected alcohol towards realizing a bromenium ion initiated spiroketalization cascade. Addition of ethanol aided an early termination of the cascade by scavenging the THP group after the halofunctionalization stage, furnishing monobromospiroketals. Alternatively, exclusion of ethanol from the reaction mixture biased the transient oxocarbenium towards α-deprotonation that precedes a second bromofunctionalization event thus, furnishing dibrominated spiroketals. The regio- and stereoselectivity exploited in the current methodology provides a novel and rapid access to the dibrominated spiroketal motifs exhibited by several natural products.