Inhibition of amyloid formation of amyloid ß (1-42), amylin and insulin by 1,5-diazacyclooctanes, a spermine-acrolein conjugate.

Amyloid aggregates of proteins are known to be involved in various diseases such as Alzheimer's disease (AD). It is therefore speculated that the inhibition of amyloid formation can play an important role in the prevention of various diseases involving amyloids. Recently, we have found that acrolein reacts with polyamines, such as spermine, and produces 1,5-diazacyclooctane, such as cyclic spermine (cSPM). cSPM could suppress the aggregation of amyloid ß 1-40 (Aß40), one of the causative proteins of AD. This result suggests the potential inhibitory effect of cSPM against Aß 1-42 (Aß42) and other amyloid protein aggregation which are the main pathological features of AD and other diseases. However, the effect on the aggregation of such proteins remains unclear. In this study, the effect of cSPM on the amyloid formation of Aß42, amylin, and insulin was investigated. These three amyloidogenic proteins forming amyloids under physiological conditions (pH 7.4 and 37℃) served as model and are thought to be the causative proteins of AD, type 2 diabetes, and insulin-derived amyloidosis, respectively. Our results indicate that cSPM can suppress the amyloid aggregation of these proteins and reduce cytotoxicity. This study contributes to a better understanding of means to potentially counteract diseases by the means of polyamine and acrolein.

Enantioselective synthesis of cyclic and linear diamines by imine cycloadditions.

Imine is one of the most versatile functional groups in chemistry and biochemistry fields. Although many biochemical reactions involve imine formation, the inherently unstable property of N-alkyl-α,ß-unsaturated imines still hindered their utilization in organic synthesis. In this article, we described that the N-alkyl-α,ß-unsaturated imines, which prepared from alkylamines and acrolein, could smoothly react through [4 + 4] cycloaddition to give eight-membered diazacyclooctane derivatives in excellent yields. Under a similar condition, in the presence of formaldehyde, the [4 + 2] and [4 + 2 + 2] cycloadditions could lead to the formation of six-membered hexahydropyrimidine or eight-membered triazacyclooctanes, depending on the substituent of aldehydes. Moreover, an easy functional group manipulation of the cyclic products obtained from these cycloadditions can provide variously substituted chiral linear diamines. We can utilize these novel reactivities to reveal the unknown and essential properties of many biological processes that involve N-alkyl-unsaturated imines.

Facile Access to Optically Active 2,6-Dialkyl-1,5-Diazacyclooctanes.

The chiral substituted 1,5-diazacyclooctane (1,5-DACO) is of considerable importance and has attracted attention from a wide range of fields due to their unique chemical and biological properties. Despite the application potential, further study has not been optimized due to difficulties in their synthetic accessibility. Here, we report that the 1,5-DACO bearing a chiral auxiliary obtained from the formal [4+4] cycloaddition of N-alkyl-α,ß-unsaturated imines can be further derivatized by nucleophilic alkylation to give various chiral substituted 1,5-DACO derivatives. The removal of the chiral auxiliary was effectively carried out using hydrogenation over Pearlman's catalyst. This methodology allows the production of a broad range of unprecedented optically active 2,6-dialkyl-1,5-DACO, which could not be accessed by other methods.

Imino [4+4] cycloaddition products as exclusive and biologically relevant acrolein-amine conjugates are intermediates of 3-formyl-3,4-dehydropiperidine (FDP), an acrolein biomarker.

We demonstrated synthetically that the eight-membered heterocycles 2,6,9-triazabicyclo[3.3.1]nonanes and 1,5-diazacyclooctanes are the initial and exclusive products of the reaction, through an imino [4+4] cycloaddition, of biologically relevant amines with acrolein. The stabilities of the aminoacetals within the eight-membered heterocycles determined whether the product was subsequently transformed gradually into the 3-formyl-3,4-dehydropiperidine (FDP), which is widely used as an oxidative stress marker. The reactivity profiles discovered in this study suggested that some of the imino [4+4] cycloaddition products are reactive intermediates of FDP and contribute to the mechanisms underlying the oxidative stress response to acrolein.