Investigating the diastereoselective synthesis of a macrocycle under Curtin-Hammett control.

This work sheds new light on the stereoselective synthesis of chiral macrocycles containing twisted aromatic units, valuable π-conjugated materials for recognition, sensing, and optoelectronics. For the first time, we use the Curtin-Hammett principle to investigate a chiral macrocyclisation reaction, revealing the potential for supramolecular π-π interactions to direct the outcome of a dynamic kinetic resolution, favouring the opposite macrocyclic product to that expected under reversible, thermodynamically controlled conditions. Specifically, a dynamic, racemic perylene diimide dye (1 : 1 P : M) is strapped with an enantiopure (S)-1,1'-bi-2-naphthol group (P-BINOL) to form two diastereomeric macrocyclic products, the homochiral macrocycle (PP) and the heterochiral species (PM). We find there is notable selectivity for the PM macrocycle (dr = 4 : 1), which is rationalised by kinetic templation from intramolecular aromatic non-covalent interactions between the P-BINOL π-donor and the M-PDI π-acceptor during the macrocyclisation reaction.

Subacromial contact after acromioplasty in the rotator cuff deficient shoulder.

Subacromial impingement (SAI) is associated with shoulder pain and dysfunction and is exacerbated by rotator cuff tears; however, the role of acromioplasty in mitigating subacromial contact in the rotator cuff deficient shoulder remains debated. This study aimed to quantify the influence of isolated and combined tears involving the supraspinatus on subacromial contact during abduction; and second, to evaluate the influence of acromioplasty on joint space size and subacromial contact under these pathological conditions. Eight fresh-frozen human cadaveric upper limbs were mounted to a computer-controlled testing apparatus that simulated joint motion by simulated force application. Shoulder abduction was performed while three-dimensional joint kinematics was measured using an optoelectronic system, and subacromial contact evaluated using a digital pressure sensor secured to the inferior acromion. Testing was performed after an isolated tear to the supraspinatus, as well as tears involving the subscapularis and infraspinatus-teres minor, both before and after acromioplasty. Rotator cuff tears significantly increased peak subacromial pressure (p < 0.001), average subacromial pressure (p = 0.001), and contact force (p = 0.034) relative to those in the intact shoulder. Following acromioplasty, significantly lower peak subacromial contact pressure, force and area were observed for all rotator cuff tears involving the supraspinatus at 30° of abduction (p < 0.05). Acromioplasty predominantly reduces acromion thickness anteriorly thereby reducing subacromial contact in the rotator cuff deficient shoulder, particularly in early to mid-abduction where superior glenohumeral joint shear force potential is large. These findings provide a biomechanical basis for acromioplasty as an intervention for SAI syndrome and as an adjunct to rotator cuff repairs.

N-Acetylcolchinol Methyl Ether (a Natural Product); Suhailamine (a Phantom Natural Product).

The reported characterization data for the allocolchicinoid alkaloid suhailamine, isolated from Colchicum decaisnei and known to have an erroneous structure, have been reanalyzed. This analysis has led to the current proposal that suhailamine has the same structure as N-acetylcolchinol methyl ether (NCME), an assertion that is supported by comparison with previously reported data for NCME. Suhailamine is therefore a phantom natural product, while NCME represents a naturally occurring allocolchicinoid rather than a purely synthetic entity.