Carreira and Fessard explore synthetic strategies and opportunities related to four-membered ring-containing spirocycles. The topics addressed include methodoloy for data mining, general methods for ...the formation of small rings, synthetic strategies toward the synthesis of spiro3,nalkanes, and current chemical space of spirocyclic systems.
Saturated bicycles are becoming ever more important in the design and development of new pharmaceuticals. Here a new strategy for the synthesis of bicyclo2.1.1hexanes is described. These bicycles ...are significant because they have defined exit vectors, yet many substitution patterns are underexplored as building blocks. The process involves sensitization of a bicyclo1.1.0butane followed by cycloaddition with an alkene. The scope and mechanistic details of the method are discussed.
Aromatic ring isosteres and rigidified saturated hydrocarbons are important motifs to enable drug discovery. Herein we disclose 2-ladderanes as a class of meta-substituted aromatic ring isosteres and ...rigidified cyclohexanes. A straightforward synthesis of the building blocks is presented along with representative derivatization. Preliminary studies reveal that the 2-ladderanes offer similar metabolic and physicochemical properties thus establishing this class of molecules as interesting motifs.
Bicycloalkyl groups have been previously described as phenyl group bioisosteres. This article describes the synthesis of new building blocks allowing their introduction into complex molecules, and ...explores their use as a means to modify the physicochemical properties of drug candidates and improve the quality of imaging agents. In particular, the replacement of an aromatic ring with a bicyclo1.1.1pentane‐1,3‐diyl (BCP) group improves aqueous solubility by at least 50‐fold, and markedly decreases nonspecific binding (NSB) as measured by CHI(IAM), the chromatographic hydrophobicity index on immobilized artificial membranes. Structural variations with the bicyclo2.2.2octane‐1,4‐diyl group led to more lipophilic molecules and did not show the same benefits regarding NSB or solubility, whereas substitutions with cubane‐1,4‐diyl showed improvements for both parameters. These results confirm the potential advantages of both BCP and cubane motifs as bioisosteric replacements for optimizing para‐phenyl‐substituted molecules.
Lifting the fog: Many drug and tracer candidates contain para‐substituted phenyl groups, and we show that their physicochemical properties can be improved by bioisosteric substitutions. While bicyclo2.2.2octyl has properties similar to those of para‐phenyl, the use of bicyclo1.1.1.pentyl and cubane‐1,4‐diyl leads to strongly increased water solubility, and to a marked decrease in nonspecific binding (NSB). This is particularly important for PET imaging tracers, as the lower the NSB signal, the less “foggy” images will be.
Despite the variety of energetic polyoxetane binders, the oxirane-based glycidyl azide polymer (GAP) has largely succeeded in the market due to its advantageous properties. Nevertheless, it suffers ...from various drawbacks such as non-uniform chain termination, possible chlorine content (flame retardant), and toxic epichlorohydrin required for its synthesis. These problems can be bypassed using the structurally related poly(3-azidooxetane). Unfortunately, it is only accessible in moderate yield by polymerization of 3-azidooxetane. Herein, we describe its synthesis by polymer-analogous transformation using the new polymers poly(3-tosyloxyoxetane) and poly(3-mesyloxyoxetane) as precursors. This results in a significantly increased yield and improved safety as handling of the very sensitive 3-azidooxetane is avoided. The aforementioned prepolymers were prepared using boron trifluoride etherate as well as triisobutylaluminum as catalysts. The latter provides polymers of particularly high molecular weight, and the corresponding poly(3-azidooxetane) species was obtained and studied for the first time. In order to shed light on the applicability of poly(3-azidooxetane) as a GAP substitute, it was thoroughly studied with regard to thermal behavior, energetic performance (EXPLO5), plasticizer compatibility, and curing. Moreover, the aquatic toxicity of all involved monomers was analyzed and compared to epichlorohydrin. Here, poly(3-azidooxetane) turned out as a fully adequate, if not more environmentally benign, substitute.
The synthesis of novel oxetanyl peptides, where the amide bond is replaced by a non-hydrolyzable oxetanylamine fragment, is reported. This new class of pseudo-dipeptides with the same H-bond ...donor/acceptor pattern found in proteins expands the repertoire of peptidomimetics.
Bicycloalkanes are well‐known isosteres of alkynes and aromatic rings and their use in the field of medicinal chemistry and drug discovery has been on the rise in the past ten years. Herein, we ...report the modular and practical synthesis of bicycloalkane‐containing fragments using nickel‐photoredox catalysis. The comparison of their relevant physical‐chemical properties with their aromatic counterparts shows a substantial improvement in LogP and aqueous solubility for bicyclo1.1.1pentane derivatives, but not for bicyclo2.2.2octane derivatives.
3-Substituted oxetanes are valuable monomers for modern ring-opening polymerizations. A new solid-state oxidizer, 3,3-dinitratooxetane (C
3
H
4
N
2
O
7
), which has an oxygen content of 62.2% was ...synthesized by the addition of N
2
O
5
to oxetan-3-one. Monoclinic single crystals suitable for X-ray diffraction (
ρ
1.80 g cm
−3
) were obtained by recrystallization from dichloromethane. In addition, 3-nitratooxetane was prepared by an improved method and 3-nitrato-3-methyloxetane was synthesized for the first time. Theoretical calculations were computed by the EXPLO5 software and additionally sensitivities towards impact and friction were determined.
3,3-Dinitratooxetane was prepared by the addition of dinitrogen pentoxide to oxetan-3-one and a crystal structure was obtained. Hot plate test of 3,3-dinitratooxetane (
1
).
Highly oxygenated cyclohexanes, including (amino)cyclitols, are featured in natural products possessing a notable range of biological activities. As such, these building blocks are valuable tools for ...medicinal chemistry. While de novo synthetic strategies have provided access to select compounds, challenges including stereochemical density and complexity have hindered the development of a general approach to (amino)cyclitol structures. This work reports the use of arenophile chemistry to access dearomatized intermediates which are amenable to diverse downstream transformations. Practical guidelines were developed for the synthesis of natural and non‐natural (amino)cyclitols from simple arenes through a series of strategic functionalization events.
This work presents a systematic approach for accessing complex natural and non‐natural (amino)cyclitols from simple arenes. A key feature includes the application of a dearomative functionalization with arenophiles and subsequent diversification, generating a widespread library of compounds spanning far into underexplored chemical space.
Energetic oxetanes were first described in the 1970s, such as 3,3‐bis(azidomethyl)oxetanes (BAMO) and 3‐(nitratomethyl)‐3‐(methyl)oxetanes (NIMMO). Over the past few years, oxetanes were hardly ...available only as special‐purpose chemicals for the pharmaceutical industry. Oxetan‐3‐one is condensed with energetic compounds with a hydrazino function such as amino‐nitroguanidine and picryl hydrazine to form energetic Schiff bases. Hydrazinolysis of the guanidine derivatives lead to energetic spiro‐tetrahydrotetrazines which are quite rare in literature. All products were characterized by their crystal structure using single‐crystal X‐ray diffraction. Furthermore, the new compounds were analyzed using IR, EA, DTA, and multinuclear NMR spectroscopy (1H and 13C). The sensitivities towards external stimuli such as friction and impact were determined according to BAM standards and the energetic performances were calculated using the EXPLO5 code.
Carbonyl functions such as ketones and aldehydes are extremely versatile chemical groups. Oxetan‐3‐one is functionalized via condensation with energetic compounds having a hydrazino function to form Schiff bases. Further functionalization with hydrazine lead to several unexpected but energetic spiro‐tetrahydrotetrazines which were characterized by their X‐ray structure.
![Strain-Release [2π + 2σ] Cy...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0002-7863_1943-2984_1520-5126/small "Strain-Release [2π + 2σ] Cycloadditions for the Synthesis of Bicyclo[2.1.1]hexanes Initiated by Energy Transfer")
![[2]-Ladderanes as isosteres...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/2041-1723/small "[2]-Ladderanes as isosteres for meta-substituted aromatic rings and rigidified cyclohexanes")
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