Facile synthesis of the glucosylceramide synthase inhibitor GZ667161

Highlights

• GZ161 is an important tool molecule that is not commercially available.

• The published synthesis of GZ161 failed to provide sufficient quantities for our needs.

• Moving the Suzuki reaction to the beginning increased the overall yield to 30%.

• 2D-COZY, HMBC and HSQC NMR were used to nequivocally assign the structure of GZ161.

Abstract

GZ667161 (GZ-161) is a quinuclidine-based small molecule inhibitor of the lysosomal enzyme glucosylceramide synthase. It represents an important tool molecule for studying the contribution of glycosphingolipids to disease pathology in lysosomal storage disorders such as Gaucher disease and GBA1 Parkinson’s disease. GZ667161 is not commercially available. The published synthesis involves 6 steps and proceeds in 18% overall reported yield. As part of a drug discovery program targeting Type 2 Gaucher disease we required quantities of GZ667161 that would support animal studies. To facilitate the project, we devised and executed an efficient 4-step convergent synthesis of the compound.

Introduction

Gaucher disease is the most common liposomal storage disorder, with a prevalence of 1 in 57,000 births [1]. Patients possess deleterious mutations in the GBA1 gene encoding the lysosomal enzyme glucocerebrosidase (Gcase). Deficient or loss of Gcase activity results in accumulation of its substrates glucosylceramide and glucosylsphingosine in diseased tissues. Type 2 Gaucher disease is a variant that affects the neurological system, causing severe and irreversible brain damage during the first years of life. Additionally, accumulation of Gcase substrates in the brain stem may play a pathological role in the neurodegeneration associated with Parkinson’s disease [2]. With no drugs approved for their treatment, Type 2 Gaucher disease and GBA-Parkinson’s disease are highly unmet medical needs.

One of the current avenues under investigation for the treatment of Gaucher disease is preventing the synthesis of Gcase substrates. To accomplish this, the enzyme that produces glucosylceramide from ceramide, glucosylceramide synthase (GCS), has been targeted for inhibition. The quinuclidine analog GZ667161 (GZ-161, 1, Fig. 1) [3] is an inhibitor of GCS. It has become an important tool molecule that is used to study the contribution of glycosphingolipids to disease pathology. The compound acts to reduce substrate flux into biosynthetic sphingolipid pathways. In a neuronopathic Gaucher disease mouse model, GZ667161 reduced brain glucosylceramide and glucosylsphingosine levels and significantly extended lifespan [4].

In a Gaucher-related synucleinopathy mouse model, GZ667161 also decreased α-synuclein and improved cognition in the mice [3]. Alpha-synuclein has also been implicated in the disease pathology of Parkinson’s disease [5]. Recently, 1 has been shown to slow the accumulation of hippocampal aggregates of α-synuclein, ubiquitin, and tau, and improved the associated memory deficits [3].

As part of a drug discovery program targeting Type 2 Gaucher disease we required quantities of 1 to support in vitro and in vivo studies. The lack of a commercial supply of the molecule prompted us to synthesize it. The only published synthesis of GZ667161 appears in the patent literature [6], [7]. However, in our hands, the published procedure failed to produce adequate quantities of 1 to meet our needs. We therefore designed and successfully carried out a modified synthesis of 1. Our results are presented herein.