Search

We recently designed guanidine-bridged nucleic acids (GuNA), and GuNA bearing a thymine (T) nucleobase was synthesized and successfully incorporated into oligonucleotides. The GuNA-T-modified oligonucleotides possessed high duplex-forming ability towards their complementary single-stranded RNAs and were highly stable against 3'-exonuclease. Therefore, GuNA is a promissing artificial nucleic acid for therapeutic antisense oligonucleotides. We herein report the facile synthesis of GuNA phosphoramidites bearing adenine (A), guanine (G), and 5-methylcytosine (mC) nucleobases and a robust method for the preparation of GuNA-modified oligonucleotides, even with sequences having acid-sensitive purine nucleobases. Oligonucleotides modified with GuNA-A, -G, or -mC possessed high duplex-forming ability, similar to those modified with GuNA-T. Moreover, some of the GuNA-modified oligonucleotides were revealed to have high base discriminating ability compared with that of their natural counterparts. GuNA nucleosides exhibited no genotoxicity in bacterial reverse mutation assays. Thus, all GuNAs (GuNA-T, -A, -G, and -mC) are now available to be examined in therapeutic applications.

In this study, research and development for the synthetic process of a PDE10A inhibitor are described; in particular, an efficient regioselective construction of the quinoxaline unit, a cost-effective pyrazolo[1,5-a]pyrimidine formation, and a cost-saving approach in a nucleophilic aromatic substitution (SNAr) reaction by introducing oxazolidinone as an electron-withdrawing group to a chloropyrazolo[1,5-a]pyrimidine core are key points. The newly developed process has been successfully scaled up to 40 kg. Furthermore, a one-pot tandem reaction from aminopyrazole to dichloropyrazolo[1,5-a]pyrimidine by activating malonic acid with POCl3 was discovered. The finding contributed to avoiding isolation of the hygroscopic pyrazolo[1,5-a]pyrimidin-5(4H)-one intermediate, which caused complicated filtration and drying processes observed in the first scale-up campaign.

We have developed a new class of PDE10A inhibitor, a pyrazolo[1,5-a]pyrimidine derivative MT-3014 (1). A previous compound introduced was deprioritized due to concerns for E/Z-isomerization and glutathione-adduct formation at the core stilbene structure. We discovered pyrazolo [1,5-a] pyrimidine as a new lead scaffold by structure-based drug design utilizing a co-crystal structure with PDE10A. The lead compound was optimized for in vitro activity, solubility, and selectivity against human ether-a-go-go related gene cardiac channel binding. We observed that MT-3014 shows excellent efficacy in rat conditioned avoidance response test and suitable pharmacokinetic properties in rats, especially high brain penetration.

A transglycosylation reaction of 2′-amino-locked nucleic acid (LNA) from thymine (T) to other nucleobases adenine (A), guanine (G), and 5-methylcytosine (mC) has been developed. This reaction proceeds in high yield and with high β-selectivity. The mild reaction conditions enable the coexistence of acid-labile protecting groups, including a 4,4′-dimethoxytrytyl (DMTr) group. 2′-Amino-LNAs bearing any nucleobase can now be easily synthesized.