A Straightforward Synthesis of Six‐Membered‐Ring Heterocyclic α‐Aminophosphonic Acids from N ‐Acyliminium Ions

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Stereocontrolled Synthesis of Phosphoproline Analogues Containing a trans-Fused Octahydroindole Bicyclic System

Herein we report for the first time the diastereoselective synthesis of (2R,3aR,7aS)- and (2S,3aS,7aR)-octahydroindole-2-phosphonic acid (OicP trans-fused stereoisomers) from diethyl (R)- and (S)-phosphopyroglutamate derivative. The key steps of this procedure are the ruthenium tetroxide oxidation of enantiomerically pure diethyl (R)- and (S)-phosphoprolinate obtained through Katritzky's benzotriazole-oxazolidine methodology, a highly diastereoselective successive double 4,5-diallylation of diethyl (R)- and (S)-phosphopyroglutamate with allyl bromide and allyltrimethylsilane with a trans-addition mode, and a ring-closing metathesis with Grubbs' first-generation ruthenium catalyst.

An efficient synthesis of cis-4-hydroxyphosphonic and cis-4-hydroxyphosphinic analogs of pipecolic acid from cyclic enaminones

An expedient synthetic entry to cis-4-hydroxyphosphonic and cis-4-hydroxyphosphinic analogs of cis-4-hydroxypipecolic acid is presented in this paper. The main feature of this methodology is the highly regioselective addition of silyl phosphites or phosphonites to cyclic 1-benzyloxycarbonyl enaminones. Interestingly, the hydride reduction of the resulting 2-phospho-4-oxopiperidine proceeds with high diastereofacial preference using NaBH₄. In the last step, the cleavage of N-Cbz group under hydrogenolysis followed by the hydrolysis of the phosphonate or phosphinate functionalities, led to the target cis-4-hydroxyphosphonic and cis-4-hydroxyphosphinic acids, respectively.

A One-Pot Approach to 2-Substituted-2-(Dimethoxyphosphoryl)-Pyrrolidines from Substituted tert-Butyl 4-Oxobutylcarbamates and Trimethyl Phosphite

A novel approach to 2-substituted-2-(dimethoxyphosphoryl)-pyrrolidines 7a-7o and 9a-9r has been developed, which features a TMSOTf-mediated one-pot intramolecular cyclization and phosphonylation of substituted tert-butyl 4-oxobutylcarbamates. The major advantages of this method include simple operation under mild reaction conditions, the use of cheap Lewis acid, and good to excellent yields with high diastereoselectivities (dr up to 99:1).

New approaches towards the synthesis of 1,2,3,4-tetrahydro isoquinoline-3-phosphonic acid (TicP)

Two new strategies for the efficient synthesis of racemic 1,2,3,4-tetrahydroisoquinoline-3-phosphonic acid (Tic^P) (±)-2 have been developed. The first strategy involves the electron-transfer reduction of the easily obtained α,β-dehydro phosphonophenylalanine followed by a Pictet-Spengler cyclization. The second strategy involves a radical decarboxylation-phosphorylation reaction on 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic). In both strategies, the highly electrophilic N-acyliminium ion is formed as a key intermediate, and the target compound is obtained in good yield using mild reaction conditions and readily available starting materials, complementing existing methodologies and contributing to the easy accessibility of (±)-2 for further research.