Synthesis and biological study of new galanthamine-peptide derivatives designed for prevention and treatment of Alzheimer's disease

The Alzheimer's disease leads to neurodegenerative processes and affecting negatively million people worldwide. The treatment of the disease is still difficult and incomplete in practice. Galanthamine is one of the most commonly used drugs against the illness. The main aim of this work is design and synthesis of new derivatives of galanthamine comprising peptide moiety as well as study of their β-secretase inhibitory activity and the anti-aggregating effect. All new derivatives of galanthamine containing analogues of Leu-Val-Phe-Phe (Aβ17-Aβ20) were synthesized in solution using fragment and consecutive condensation approaches. The new derivatives were characterized by melting points, NMR, and HPLC/MS. They were tested in vitro for β-secretase inhibition activity by means of fluorescent method and were investigated in vitro for anti-aggregation activity on sheep platelet-rich plasma. Although the new compounds do not contain a structural element responsible for the β-secretase inhibition, five of them show high or good β-secretase inhibitory activity between 19.98 and 51.19% with IC₅₀ between 1.95 and 5.26 nM. Four of the new molecules were able to inhibit platelet aggregation between 55.0 and 90.0% with IC₅₀ between 0.69 and 1.36 µM. Four of the compounds were able to inhibit platelet aggregation and two of them have high anti-aggregating effects.

Stereoselective yeast-mediated reduction of trans-5-(1'-oxo-3'-methylbutyl)-3-methyldihydrofuran-2-one: production of chiral intermediates for the synthesis of β-secretase inhibitors

OBJECTIVE

To investigate the usefulness of yeast strains to the production of chiral hydroxylactones, important synthons in the synthesis of β-secretase inhibitors.

RESULTS

Strains Rhodotorula glutinis KCh 242, Rhodotorula rubra KCh 82, Rhodotorula marina KCh 77 and Saccharomyces cerevisiae KCh 464 reduced racemic trans-5-(1'-oxo-3'-methylbutyl)-3-methyldihydrofuran-2-one (4) according to the Prelog's rule to afford preferentially the stereoisomers with S configurations at C-1'. R. marina KCh 77 and R. glutinis KCh 242 exhibited selectivity towards 3S, 5R enantiomer of the substrate, whereas R. rubra KCh 82 and S. cerevisiae KCh 464 preferred the reduction of its antipode. The highest yield of 3R,5S,1'S-hydroxylactone 3c (78 %) was obtained with R. rubra KCh 82.

CONCLUSIONS

Different stereoisomers of trans-5-(1'-hydroxy-3'-methylbutyl)-3-methyldihydrofuran-2-one and its 5-substituted analogues are produced as important intermediates in the synthesis of drugs for the therapy of Alzheimer's disease.

Therapeutic strategies for Alzheimer's disease in clinical trials

Alzheimer's disease (AD) is considered to be the most common cause of dementia and is an incurable, progressive neurodegenerative disorder. Current treatment of the disease, essentially symptomatic, is based on three cholinesterase inhibitors and memantine, affecting the glutamatergic system. Since 2003, no new drugs have been approved for treatment of AD. This article presents current directions in the search for novel, potentially effective agents for the treatment of AD, as well as selected promising treatment strategies. These include agents acting upon the beta-amyloid, such as vaccines, antibodies and inhibitors or modulators of γ- and β-secretase; agents directed against the tau protein as well as compounds acting as antagonists of neurotransmitter systems (serotoninergic 5-HT6 and histaminergic H3). Ongoing clinical trials with Aβ antibodies (solanezumab, gantenerumab, crenezumab) seem to be promising, while vaccines against the tau protein (AADvac1 and ACI-35) are now in early-stage trials. Interesting results have also been achieved in trials involving small molecules such as inhibitors of β-secretase (MK-8931, E2609), a combination of 5-HT6 antagonist (idalopirdine) with donepezil, inhibition of advanced glycation end product receptors by azeliragon or modulation of the acetylcholine response of α-7 nicotinic acetylcholine receptors by encenicline. Development of new effective drugs acting upon the central nervous system is usually a difficult and time-consuming process, and in the case of AD to-date clinical trials have had a very high failure rate. Most phase II clinical trials ending with a positive outcome do not succeed in phase III, often due to serious adverse effects or lack of therapeutic efficacy.