Cp2TiCl2-Catalyzed Photoredox Allylation of Aldehydes with Visible Light

A Barbier-type Cp2TiCl2-mediated (10 mol %) photoredox allylation of aldehydes under irradiation with visible light (blue light-emitting diodes (LEDs), 450 nm) and in the presence of an organic dye (3DPAFIPN, 5 mol %) with allylbromides is described

Stereoselective continuous-flow alkylation of aldehydes in organocatalytic packed-bed reactors

The development of efficient catalytic enantioselective \u3b1-alkylations of carbonyl compounds has been for a long time a challenging task. Among the strategies for performing this reaction, the novel synthetic methodology employing stable carbenium ions catalyzed by MacMillan type chiral organocatalysts has attracted our attention. Given our experience in the synthesis of solid-supported chiral imidazolidinones, we set up a continuous flow system for the enantioselective alkylation of aldehydes. Performing the reaction under continuous flow conditions makes the process extremely attractive because of the several advantages that continuous-flow synthetic methods offer over traditional batch ones: more accurate control of process conditions, shorter reaction times, easier isolation of final products and straightforward scale-up. Silica-supported (A) and Polystyrene-supported (B) catalysts were synthesized and two packed-bed reactors were prepared. The first example of stereoselective continuous-flow \u3b1-alkylation of various aldehydes with 1,3-benzodithiolylium tetrafluoroborate was performed in flow reactors at room temperature affording the products with great productivity (higher than those obtained with homogenous catalyst) and excellent enantioselectivity

(Hydroxyphenyl)oxazoline: a Novel and Remarkably Facile Entry into the Area of Chiral Cationic Alkylzirconium Complexes Which Serve as Polymerization Catalysts

How can the entry into the area of chiral cationic alkyl derivatives of group 4 metals be simplified? We succeeded in, using readily available amino alcohols, which have been converted into chiral (hydroxyphenyl)oxazolines. These compounds have been employed in the organometallic derivatization of early transition metals

Persistence of somatostatinergic tone in acromegaly

It is a matter of debate whether hypothalamic somatostatin (SRIH) secretion in acromegaly is preserved and still regulated by the physiological feedback mechanisms of growth hormone (GH) and insulin-like growth factor I. To gather further information on this, the reproducibility of plasma GH changes induced by growth hormone-releasing hormone (GHRH) administration was evaluated in 15 acromegalic patients. There was a highly significant correlation between the peak/basal ratio (P/B) GH response in the 15 patients administered GHRH on two separate occasions (r = 0.99, p < 0.001). The test was performed also before and after the administration of drugs able to inhibit or stimulate hypothalamic SRIH release, by activating (pyridostigmine) or inhibiting (pirenzepine) cholinergic pathways, respectively. The GHRH-induced GH response (P/B = 2, range 1.1-26.1) was increased significantly by pyridostigmine pretreatment in 30 patients (P/B = 2.6, range 1.3-34.8; p = 0.0045). In nine out of 30 patients an increase of greater than 2 SD of within-subject GHRH variability was observed in response to GHRH plus pyridostigmine when compared to GHRH alone. An inverse correlation (r = -0.37, p < 0.05) was observed between GH response to GHRH alone and after pyridostigmine pretreatment. On the contrary, no change of GHRH-induced GH response was observed in 12 patients after pirenzepine pretreatment (P/B = 1.9, range 1.1-5 and P/B = 2, range 1.3-6 without and after pirenzepine pretreatment, respectively). These data suggest that in acromegaly the somatostatinergic tone does not seem to fluctuate, and that it can be inhibited often by cholinergic pathway activation but not increased further by cholinergic suppression

Comparability of automated drusen volume measurements in age-related macular degeneration: a MACUSTAR study report

Drusen are hallmarks of early and intermediate age-related macular degeneration (AMD) but their quantification remains a challenge. We compared automated drusen volume measurements between different OCT devices. We included 380 eyes from 200 individuals with bilateral intermediate (iAMD, n = 126), early (eAMD, n = 25) or no AMD (n = 49) from the MACUSTAR study. We assessed OCT scans from Cirrus (200 × 200 macular cube, 6 × 6 mm; Zeiss Meditec, CA) and Spectralis (20° × 20°, 25 B-scans; 30° × 25°, 241 B-scans; Heidelberg Engineering, Germany) devices. Sensitivity and specificity for drusen detection and differences between modalities were assessed with intra-class correlation coefficients (ICCs) and mean difference in a 5 mm diameter fovea-centered circle. Specificity was > 90% in the three modalities. In eAMD, we observed highest sensitivity in the denser Spectralis scan (68.1). The two different Spectralis modalities showed a significantly higher agreement in quantifying drusen volume in iAMD (ICC 0.993 [0.991–0.994]) than the dense Spectralis with Cirrus scan (ICC 0.807 [0.757–0.847]). Formulae for drusen volume conversion in iAMD between the two devices are provided. Automated drusen volume measures are not interchangeable between devices and softwares and need to be interpreted with the used imaging devices and software in mind. Accounting for systematic difference between methods increases comparability and conversion formulae are provided. Less dense scans did not affect drusen volume measurements in iAMD but decreased sensitivity for medium drusen in eAMD

Author Correction: Comparability of automated drusen volume measurements in age-related macular degeneration: a MACUSTAR study report (vol 12, 21911, 2022)

Ophthalmic researc

Retest variability and patient reliability indices of quantitative fundus autofluorescence in age-related macular degeneration: a MACUSTAR study report

This study aimed to determine the retest variability of quantitative fundus autofluorescence (QAF) in patients with and without age-related macular degeneration (AMD) and evaluate the predictive value of patient reliability indices on retest reliability. A total of 132 eyes from 68 patients were examined, including healthy individuals and those with various stages of AMD. Duplicate QAF imaging was conducted at baseline and 2 weeks later across six study sites. Intraclass correlation (ICC) analysis was used to evaluate the consistency of imaging, and mean opinion scores (MOS) of image quality were generated by two researchers. The contribution of MOS and other factors to retest variation was assessed using mixed-effect linear models. Additionally, a Random Forest Regressor was trained to evaluate the extent to which manual image grading of image quality could be replaced by automated assessment (inferred MOS). The results showed that ICC values were high for all QAF images, with slightly lower values in AMD-affected eyes. The average inter-day ICC was found to be 0.77 for QAF segments within the QAF8 ring and 0.74 for peripheral segments. Image quality was predicted with a mean absolute error of 0.27 on a 5-point scale, and of all evaluated reliability indices, MOS/inferred MOS proved most important. The findings suggest that QAF allows for reliable testing of autofluorescence levels at the posterior pole in patients with AMD in a multicenter, multioperator setting. Patient reliability indices could serve as eligibility criteria for clinical trials, helping identify patients with adequate retest reliability

Stereoselective Reactions with Stabilized Carbocations

SN1-type reactions are ubiquitous in modern organic synthesis. Organic chemists are introduced to well-established SN1-type reactions in undergraduate courses, and the accompanying message of these lessons is the elusive stability and the high reactivity of carbocations

Diastereoselective addition of a silylketeneacetal to chiral alpha-thioaldehydes

Chiral apha-thioaldehydes 2\u20136 undergo chelation or non-chelation controlled addition of silylketene acetal 1, depending on the nature of the Lewis acid catalyst and of the ligands at the stereocenter