Search

Sugar phosphates are emerging as potential therapeutic candidates for certain diseases. However, their high polarity makes them poorly absorbed by the body and their penetration inside the cell is even more difficult without a proper transporter. Amino sugar phosphates (n‐amino‐n‐deoxy‐sugars, carbohydrates in which a hydroxyl group has been replaced with an amine group), such as N‐acetyl‐d‐mannosamine (ManNac)‐6‐phosphate have shown potential as a treatment for a muscular disease called GNE myopathy caused by a deficiency in the production of sialic acid. However, its high polarity leads to poor absorption and consequent high dosage in humans, causing unwanted side effects. Herein, we describe the application of phosphoramidate prodrug chemistry to 1,3,4‐O‐acetylated N‐acetylmannosamine (Ac3ManNAc) to deliver ManNAc‐6‐phosphate (ManNAc‐6‐P), a critical intermediate in sialic acid biosynthesis. Sialic acid deficiency is a hallmark of GNE myopathy, a rare congenital disorder of glycosylation (CDG), caused by mutations in the gene “GNE,” that limit the production of ManNAc‐6‐P. Synthetic methods were developed to provide a library of Ac3ManNAc‐6‐phosphoramidates that were evaluated in a series of studies for their potential as a treatment for GNE myopathy. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Synthesis of 2‐Acetamido‐1,3,4‐tri‐O‐acetyl‐2‐deoxy‐d‐mannopyranose. Basic Protocol 2: Preparation of 3‐acetamido‐6‐((((((S)‐1‐ethoxy‐4‐methyl‐1‐oxo‐pentan‐2‐yl) amino) (phenoxy)phosphoryl) oxy) methyl) tetrahydro‐2H‐pyran‐2,4,5‐triyl triacetate (5). Support Protocol: Preparation of ethyl (chloro(phenoxy)phosphoryl)‐l‐leucinate.

Following the first report on the nucleoside phosphoramidate (ProTide) prodrug approach in 1990 by Chris McGuigan, the extensive investigation of ProTide technology has begun in many laboratories. Designed with aim to overcome limitations and the key resistance mechanisms associated with nucleoside analogues used in the clinic (poor cellular uptake, poor conversion to the 5′-monophosphate form), the ProTide approach has been successfully applied to a vast number of nucleoside analogues with antiviral and anticancer activity. ProTides consist of a 5′-nucleoside monophosphate in which the two hydroxyl groups are masked with an amino acid ester and an aryloxy component which once in the cell is enzymatically metabolized to deliver free 5′-monophosphate, which is further transformed to the active 5′-triphosphate form of the nucleoside analogue. In this review, the seminal contribution of Chris McGuigan’s research to this field is presented. His technology proved to be extremely successful in drug discovery and has led to two Food and Drug Administration-approved antiviral agents.

Protection and deprotection strategies involving the N-acetyl group are widely utilized in nucleoside and nucleotide chemistry. Herein, we present a mild and selective N-deacetylation methodology, applicable to purine and pyrimidine nucleosides, by means of Schwartz's reagent, compatible with most of the common protecting groups used in nucleoside chemistry.

The use of pronucleotides to circumvent the well-known drawbacks of nucleotide analogs has played a significant role in the area of antiviral and anticancer drug delivery. Several motifs have been designed to mask the negative charges on the phosphorus moiety of either nucleoside monophosphates or nucleoside phosphonates, in order to increase their hydrophobicity and allow entry of the compound into the cell. Among them the bis-amidate analogs, having two identical amino acids as masking groups through a P–N bond, represent a more recent approach for the delivery of nucleotide analogs, endowed with antiviral or anticancer activity. Different synthetic strategies are commonly used for preparing phosphorodiamidates of nucleosides. In this protocol, we would like to focus on the description of the synthetic methodology that in our hand gave the best results using 2′-3′-didehydro-2′-3′-dideoxythymidine (d4T, Stavudine) as model nucleoside. A second strategy for preparing diamidates of nucleoside phosphonates will be reported using {[2-(6-amino-9 H-purin-9-yl)ethoxy]methyl}phosphonic acid (PMEA, adefovir) as model substrate.

Protection and deprotection strategies involving the N-acetyl group are widely utilized in nucleoside and nucleotide chemistry. Herein, we present a mild and selective N-deacetylation methodology, applicable to purine and pyrimidine nucleosides, by means of Schwartz's reagent, compatible with most of the common protecting groups used in nucleoside chemistry.