Development of an Efficient Route to 2-Ethynylglycerol for the Synthesis of Islatravir

The unnatural, alkyne-containing nucleoside analog islatravir (MK-8591) is synthetically accessed through a biocatalytic cascade starting from 2-ethynylglycerol as a building block. Herein, we describe the development of an efficient synthesis of this building block including the initial route, route scouting and final process development. Key challenges that have been overcome are the development of an efficient and safe acetylenic nucleophile addition to an appropriate ketone, and the identification of a 2-ethynylpropane-1,2,3-triol derivative with favorable physical properties. An acid-catalyzed cracking of commercially available 1,3-dihydroxyacetone dimer and subsequent 1,2-addition of an acetylenic nucleophile has been discovered and optimized into the manufacturing process

Development of an Efficient Route to 2-Ethynylglycerol for the Synthesis of Islatravir

The unnatural, alkyne-containing nucleoside analog islatravir (MK-8591) is synthetically accessed through a biocatalytic cascade starting from 2-ethynylglycerol as a building block. Herein, we describe the development of an efficient synthesis of this building block including the initial route, route scouting and final process development. Key challenges that have been overcome are the development of an efficient and safe acetylenic nucleophile addition to an appropriate ketone, and the identification of a 2-ethynylpropane-1,2,3-triol derivative with favorable physical properties. An acid-catalyzed cracking of commercially available 1,3-dihydroxyacetone dimer and subsequent 1,2-addition of an acetylenic nucleophile has been discovered and optimized into the manufacturing process

Enantiodivergent Formation of C–P Bonds: Synthesis of P-Chiral Phosphines and Methyl-phosphonate Oligonucleotides

<p>A simple limonene-derived P(V)-based reagent for the modular, scalable, and stereospecific synthesis of chiral phosphines and methyl-phosphonate oligonucleotide (MPO) building blocks is presented. Built on a translimonene oxide (TLO) core, this formally triply electrophilic reagent class displays starkly differing reactivity from the cis-limonene oxide derived reagents reported previously [dubbed phosphorus-sulfur incorporation reagents or Ψ (PSI) for short]. These new phosphorus-incorporation reagents (PI, abbreviated as Π) access distinctly different chemical space than Ψ. The P(V)-manifold disclosed herein permits the stereochemically controlled sequential addition of carbon-based nucleophiles (from one to three) to produce a variety of enantiopure C–P bearing building blocks. When three carbon nucleophiles are added, useful P-chiral phosphines can be accessed after stereospecific reduction. When a single methyl group is added, the remaining nucleophiles can be nucleosides thus opening the door to the first stereospecific access to MPO-based oligonucleotide building blocks. Although both enantiomers of Π are available, only one isomer is required as the order of nucleophile addition controls the absolute stereochemistry of the final product through a unique enantiodivergent design.</p>

Enantiodivergent Formation of C–P Bonds: Synthesis of P-Chiral Phosphines and Methyl-phosphonate Oligonucleotides

<p>A simple limonene-derived P(V)-based reagent for the modular, scalable, and stereospecific synthesis of chiral phosphines and methyl-phosphonate oligonucleotide (MPO) building blocks is presented. Built on a translimonene oxide (TLO) core, this formally triply electrophilic reagent class displays starkly differing reactivity from the cis-limonene oxide derived reagents reported previously [dubbed phosphorus-sulfur incorporation reagents or Ψ (PSI) for short]. These new phosphorus-incorporation reagents (PI, abbreviated as Π) access distinctly different chemical space than Ψ. The P(V)-manifold disclosed herein permits the stereochemically controlled sequential addition of carbon-based nucleophiles (from one to three) to produce a variety of enantiopure C–P bearing building blocks. When three carbon nucleophiles are added, useful P-chiral phosphines can be accessed after stereospecific reduction. When a single methyl group is added, the remaining nucleophiles can be nucleosides thus opening the door to the first stereospecific access to MPO-based oligonucleotide building blocks. Although both enantiomers of Π are available, only one isomer is required as the order of nucleophile addition controls the absolute stereochemistry of the final product through a unique enantiodivergent design.</p>

Synthesis of 1-Palmitoyl-2-((E)-9- and (E)-10-nitrooleoyl)-sn-glycero-3-phosphatidylcholines

Extensive investigation of nitrated phospholipids in connection with various biologically important processes requires reliable access to suitable material. A selective chemical synthesis introducing a defined nitrofatty acid at the sn-2 position of a 2-lyso sn-glycero-3-phosphatidylcholine was developed. Given that the nitroalkene moiety of both reactant nitrofatty acid derivative and the product esters is characterised by particular sensitivity to nucleophile addition and, depending on the intermediate, subsequent olefin isomerisation and retro-Henry-type reaction, a reliable two-step ester formation was introduced. The activation of the nitrofatty acid succeeded after reaction with trichlorobenzoyl chloride, and the mixed anhydride could be isolated via extractive work-up. Subsequent reaction with 1-palmitoyl-2-lyso-sn-glycero-3-phosphatidylcholine enabled the sn-2 esterification to be achieved with high yield by using a minimum of reagents, avoiding the formation of side products and facilitating final isolation and purification.

Polyamidoamines (PAAs) functionalized with siloxanes as wood preservatives against fungi and insects

A novel treatment based on polyamidoamines (PAAs) for the preservation of wood against fungi and insects with a broad protection functionality, low effective concentration, and low environmental impact has been developed. PAAs were synthesized by nucleophile addition of ethanolamine (EtA) and/or 3-aminopropyltriethoxysilane (APTES) to N,N′-methylene-bisacrylamide (MBA). The molar ratios in the tested formulation were: I) MBA:EtA=1:1; II) MBA:APTES=1:1; III) MBA:EtA:APTES=1:0.5:0.5. These formulations, characterized by ESI-MS, NMR, FT-IR, were tested against: (a) the wood decay fungi (Coniophora puteana, Coriolus versicolor, and Poria placenta); (b) the subterranean termite Reticulitermes lucifugus, and the drywood termite Kalotermes flavicollis; (c) the woodborer Stegobium paniceum. Tests in combination with leaching showed that formulation II and III can be utilized as fungal wood preservatives for use classes 2–3 (EN 335:2013). In addition, all PAAs formulations were equally effective in preserving wood against the subterranean termite, and formulation II was most effective against drywood termite. On the other hand, the formulation I showed good efficacy against S. paniceum.

Swain–Scott relationships for nucleophile addition to ring-substituted phenonium ions

The products of the reactions of 2-(4-methoxyphenyl)ethyl tosylate (MeO-1-OTs) and 2-(4-methyphenyl)ethyl tosylate (Me-1-OTs) with nucleophilic anions were determined for reactions in 50:50 (v/v) trifluoroethanol (TFE) / water at 25 °C. In many cases, the nucleophile selectivity kNu/ks ((mol/L)−1) for reactions of nucleophile and solvent, calculated from the ratio of product yields, depends upon [Nu−]. This demonstrates the existence of competing reaction pathways, which show different selectivities for reactions with nucleophiles. A 13C NMR analysis of the products of the reactions of substrate enriched with 13C at the α-carbon, X-1-[α-13C]OTs (X = −OCH3 or −Me), with nucleophilic anions in 50:50 (v/v) TFE/water at 25 °C shows the formation of X-1-[β-13C]OH, X-1-[β-13C]OCH2CF3, and X-1-[β-13C]Nu (Nu = Br, Cl, CH3CO2, or Cl2CHCO2) from the trapping of symmetrical phenonium ion reaction intermediates X-2+. The observation of excess label in the α-position, [α-13C]/[β-13C] > 1.0, for both the water and nucleophile adducts, shows that these nucleophiles also react by direct substitution at X-1-[α-13C]OTs. The ratios of product yields, [α-13C]/[β-13C], and observed nucleophile selectivity (kNu/ks)obs were used to dissect the contribution of nucleophile addition at Me-1-OTs and trapping of X-2+ to the product yields. The product yields from partitioning of the intermediate gave the nucleophile selectivity kNu/ks for X-2+. Swain–Scott plots of log(kNu/ks) are correlated by slopes of s = 0.78 and s = 0.73 for reactions of MeO-2+ and Me-2+, respectively. This shows that the sensitivity of bimolecular substitution at X-2+ to changes in nucleophile reactivity is smaller than for nucleophilic substitution at the methyl iodide.