Leonard L.

Cyclodepsipeptides constitute a structurally diverse class of natural products composed of amino acid and hydroxy acid residues interconnected through both amide and ester bonds. Among them, xylaroamide A, a cyclic heptadepsipeptide, was recently identified from an endolichenic Xylaria species via a molecular networking-guided discovery approach. Despite xylaroamide A exhibiting intriguing structural features and notable bioactivity potential, its total synthesis has thus far remained unexplored. Herein, we report the first total synthesis of xylaroamide A, achieved through a hybrid solid/solution-phase synthetic approach. The linear precursor was assembled in accordance with the native amino acid sequence via Fmoc-based solid-phase peptide synthesis, incorporating the preassembled ester fragment at a later stage of assembly. Subsequent macrocyclization took place under high-dilution conditions to furnish the target cyclodepsipeptide. The structure of the synthetic product was confirmed by means of optical rotation and NMR and MS spectroscopic analyses, which exhibited good agreement with the reported data for the natural product. This work establishes a reliable and efficient synthetic route to xylaroamide A and provides a foundation for further bioactivity and structure optimization investigations.

Background Prion disease and Alzheimer disease (AD) are common causes of rapidly progressive dementia (RPD). Although most patients with prion disease are distinguished by MRI and CSF findings, selected cases mimic rapidly progressive AD. We characterized AD-prion disease mimics within a prospective cohort and the extant literature to identify the clinical features and tests that support accurate diagnoses in these patients. Methods Patients with prion disease initially diagnosed as rapidly progressive AD were identified from a prospective cohort study at Mayo Clinic (February 2020–June 2026) and through systematic review of MEDLINE and Embase. Results Of 204 patients with RPD, five (2.5%) were initially diagnosed with clinically probable AD but ultimately determined to have prion disease. Systematic review identified 10 additional cases (n=15, median age-at-onset, 59 years; 67% male). Presentations reproduced amnestic (53%), dysexecutive (27%), primary progressive aphasia (13%), and posterior cortical atrophy (7%) AD phenotypes; median time from AD diagnosis to consideration of prion disease was 2 months. Diffusion-weighted MRI abnormalities were absent in Mayo Clinic cases and absent/equivocal (n=2) or overlooked (n=8) in published cases. CSF biomarkers were consistent with AD in 6/9 tested patients, with elevated total tau levels in 11/13 patients and total-tau/p hosphorylated-tau181 ratios in 5/9 patients. Real-time quaking-induced conversion assays for prions were positive in the CSF of 9/12 patients. Prion disease was confirmed by neuropathology (n=7), genetics (n=2), or real-time quaking-induced conversion (n=6) assays. Conclusions Prion disease may rarely mimic rapidly progressive AD. Disproportionate elevations in CSF total-tau levels or total-tau/p hosphorylated-tau181 ratios should prompt consideration of prion disease.

Cell membranes undergo biophysical remodeling as an adaptation to the surroundings and to perform specific biological functions.