Phosphonate Chemistry and Reagents in the Synthesis of Biologically Active and Natural Products

Chiral α-Aminophosphonates as Ligands in Copper-Catalyzed Asymmetric Oxidative Coupling of 2-Naphthols

Chiral α-aminophosphonates with adjacent carbon and phosphonate stereogenic centers have been employed as ligands in the copper-catalyzed oxidative coupling of 2-naphthols, resulting in the production of chiral BINOLs in favorable yields and moderate to good enantiomeric excess. This represents the first application of chiral P-based ligands to enable such a transformation. The synthesis of these chiral α-aminophosphonate ligands offers a significant advantage over approaches that typically necessitate elaborate synthetic processes for chiral ligand production.

Copper-catalyzed stereo- and regioselective hydrophosphorylation of terminal alkynes: scope and mechanistic study

Herein, a protocol for copper-catalyzed highly stereo- and regioselective hydrophosphorylation of terminal alkynes to E-alkenylphosphorus compounds was well developed. It represents a general and practical hydrophosphorylation method, of which diarylphosphine oxide, dialkylphosphine oxide and dialkyl phosphite all had effective P(O)H parts to react with different types of terminal alkynes. Contrary to previous air-sensitive reports, all the reactions proceeded well under air. This methodology is quite attractive owing to the high stereo- and regioselectivity, good functional group tolerance, scalability and facile late-stage derivatization of some natural product derivatives and commercially available herbicides. What's more, investigations on the reaction mechanism with deuterium-labeling experiments and DFT studies firstly disclosed the deprotonation-protonation equilibrium of terminal alkynes and P(O)H part during the catalytic hydrophosphorylation process.

A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug

Four enantiomerically pure stereoisomers of rosaprostol (1), an antiulcer drug, were efficiently synthesized from the enantiomers of 2-(dimethoxyphosphoryl)-3-hexylcyclopentanone (3) as chiral substrates. The latter were obtained by resolution of racemic 3 with (+)-(R)-1-(1-naphthyl)ethylamine. The conversion of (+)-3 into rosaprostol stereoisomer (-)-1a was accomplished in four steps in 56% overall yield. According to the same protocol, the second stereoisomer (+)-1c was obtained from (-)-3 in 55% overall yield. A slightly improved procedure of the last two steps of the transformation of (+)-3 into (-)-1a allowed an increase in the overall yield to 64%. The remaining two stereoisomers, (-)-1b and (+)-1d, were obtained from (-)-1a and (+)-1c in 71 and 68% yield, respectively, by a two-reaction sequence, in which a Mitsunobu inversion of configuration at C-5 was the key step.

Facile Synthesis and Properties of 2-λ(5)-Phosphaquinolines and 2-λ(5)-Phosphaquinolin-2-ones

Treatment of 2-ethynylanilines with P(OPh)3 gives either 2,2-diphenoxy-2-λ(5)-phosphaquinolines or 2-phenoxy-2-λ(5)-phosphaquinolin-2-ones under transition-metal-free conditions. This reaction offers access to an underexplored heterocycle, which opens up the study of the fundamental nature of the N=P(V) double bond and its potential for delocalization within a cyclic π-electron system. This heterocycle can serve as a carbostyril mimic, with application as a bioisostere for pharmaceuticals based on the 2-quinolinone scaffold. It also holds promise as a new fluorophore, since initial screening reveals quantum yields upwards of 40%, Stokes shifts of 50-150 nm, and emission wavelengths of 380-540 nm. The phosphaquinolin-2-ones possess one of the strongest solution-state dimerization constants for a D-A system (130 M(-1)) owing to the close proximity of a strong acceptor (P=O) and a strong donor (phosphonamidate N-H), which suggests that they might hold promise as new hydrogen-bonding hosts for optoelectronic sensing.

Synthesis and in vitro cytotoxicity of cross-conjugated prostaglandin A and J series and their hydroxy derivatives

The synthesis of two cross-conjugated prostaglandin analogues of known neurotrophic activity and their new hydroxy derivatives was accomplished starting from the diastereoisomeric (+)-camphor protected 3-[(dimethoxyphosphoryl)methyl]-4,5-dihydroxycyclopent-2-enones. The cytotoxicity of these compounds was determined against HeLa, K562, HL-60 human cancer cell lines and normal human cells (HUVEC). We found that NEPP11 and its C7-hydroxy derivative demonstrated high anticancer activity against the HeLa and HL-60 human cancer cell lines at concentrations ranging from 1 to 2 μM. Moreover, the C7-hydroxy derivative of NEPP11 displayed high cytotoxic selectivity between cancer cell lines and normal human cells. On the other hand, the J-type prostaglandin analogue of NEPP11 and its C13-hydroxy derivatives were much less toxic or nontoxic against the cancer and normal cells at concentrations up to 1 mM.

Synthesis and the absolute configuration of both enantiomers of 4,5-dihydroxy-3-(formyl)cyclopent-2-enone acetonide as a new chiral building block for prostanoid synthesis

The synthesis of both enantiomers of 4,5-dihydroxy-3-(formyl)cyclopent-2-enone acetonide (5) was accomplished in five steps starting from meso-tartaric acid (6). The key steps involved are preparation of the isopropylidene protected 3-[(dimethoxyphosphoryl)methyl]-4,5-dihydroxycyclopent-2-enone (9), resolution of the diastereoisomeric products 10 of the Horner reaction of racemic 9 with (R)-glyceraldehyde acetonide and the final regioselective ozonolysis of the exocyclic carbon–carbon double bond of the separated dienones 10 leading to both enantiomeric title compounds 5. The absolute configuration of both enantiomers was initially assigned based on the comparison of the chiroptical properties obtained from the DFT calculations with the experimental data and finally confirmed by X-ray analysis.

Poly(phosphonate)-mediated Horner–Wadsworth–Emmons reactions

Poly(phosphonate)s were used in Horner–Wadsworth–Emmons (HWE) reactions with aldehydes. The progress of the reaction was monitored via in situ-NMR spectroscopy. Minimal purification efforts by precipitation of the polymer are achieved.

An Efficient One-Pot Synthesis of Trialkyl 2-(Dialkoxyphosphoryl)Ethene-1,1,2-Tricarboxylates

An efficient synthesis of trialkyl 2-(dialkoxyphosphoryl)ethene-1,1,2-tricarboxylates is described. This involves the reaction of alkyl cyanoformates, dialkyl acetylenedicarboxylates, and trialkyl phosphites.

Organocatalytic asymmetric synthesis of organophosphorus compounds

240 Years have passed since the discovery of elemental phosphorus. During that time organophosphorus chemistry has emerged as an interesting and exciting field of research. Recently organophosphorus chemistry has been raised to a new level. Organophosphorus compounds have found applications in asymmetric organocatalysis for the synthesis of optically active compounds of synthetic or biological importance. The aim of this review article is to present recent contributions to this developing field of chemistry and to point out synthetic advantages of methodologies developed so far.

A one step/one pot synthesis of N,N-bis(phosphonomethyl)amino acids and their effects on adipogenic and osteogenic differentiation of human mesenchymal stem cells

The one pot reaction of amino acids with diethylphosphite and formaldehyde yielded N,N-bis(phosphonomethyl)amino acids. This synthetic route does not require harsh reagents to cleave the ester group. The molecular structures of the new compounds were determined by X-ray diffraction methods. By employing DFT calculations the hydrolysis of the intermediate phosphonic esters to the respective acids could be explained by the decreasing P-OEt bond strength for C(alpha)-bisalkylated amino acids. Biological evaluation on the adipogenic and osteogenic differentiation of mesenchymal stem cells revealed no modification of the adipocyte differentiation, but inhibition of osteoblast formation at concentrations without detectable cytotoxicity.