Enantioselective synthesis of diethyl 1-hydroxyalkylphosphonates via oxazaborolidine catalyzed borane reduction of diethyl α-ketophosphonates

Ru(II)-Catalyzed Enantioselective Transfer Hydrogenation of α-Ketophosphonates: Straightforward Access to Valuable Chiral α-Hydroxy Phosphonates

Asymmetric transfer hydrogenation (ATH) is arguably one of the most powerful tools for the synthesis of chiral compounds. Despite tremendous advances in this field, the reduction of α-ketophosphonates remains largely unexplored. Herein, we report an efficient Ru-catalyzed ATH on a broad range of α-ketophosphonates. Compared with existing methods, our approach offers as advantages mild conditions, operational simplicity, limited waste generation, broad substrate scope (26 examples), good to excellent yields (75-93%), and excellent levels of stereoinduction (from 90% to >99% ee).

Functionalization of α-hydroxyphosphonates as a convenient route to N-tosyl-α-aminophosphonates

Direct conversion of the α-hydroxyl group by para-toluenesulfonamide to yield α-(N-tosyl)aminophosphonates is reported. α-Aminophosphonates 23a,b-37a,b were obtained from the corresponding α-hydroxyphosphonates 6a,b-21a,b in the presence of K₂CO₃, via the retro-Abramov reaction of the appropriate aldehydes, 1-5. The subsequent formation of imines with simultaneous addition of diethyl phosphite provided access to the α-sulfonamide phosphonates 23a,b-37a,b with better diastereoselectivity than in the case of the Pudovik reaction. The mechanism for this transformation is proposed herein. When Cbz N-protected aziridine 9a,b and phenylalanine analogue 12a,b were exploited, intramolecular substitution was observed, leading to the corresponding epoxide 38 as the sole product, or oxazolidin-2-one 39 as a minor product. Analogous substitution was not observed in the case of proline 18a,b and serine 21a,b derivatives.

Synthesis of acylphosphonates by a palladium-catalyzed phosphonocarbonylation reaction of aryl iodides with phosphites

Acylphosphonates are conveniently synthesized from aryl iodides by a palladium-catalyzed reaction with dialkyl phosphites under an atmospheric pressure of carbon monoxide. The reaction demonstrates the first example of the use of phosphorus nucleophiles in related metal-catalyzed carbonylation reactions.

Addition of optically pure H-phosphinate to ketones: selectivity, stereochemistry and mechanism

A stability-controlled diastereoselective addition of a chiral P–H species to ketones afforded P,C-stereogenic α-hydroxyphosphinates in excellent yields and dr.

Synthesis and study of (R)- and (S)-β-hydroxyphosphonate acyclonucleosides as structural analogues of (S)-HPMPC (cidofovir)

Modification of the acyclic chain highly impacts antiviral activity and recognition by human nmpks.

Diametric stereocontrol in dynamic catalytic reduction of racemic acyl phosphonates: divergence from α-keto ester congeners

An unexpected dichotomy was observed in the Ru-catalyzed asymmetric transfer hydrogenation of acyl phosphonates: reduction proceeded from the opposite face relative to that observed in the analogous reduction of α-keto esters. The first highly selective catalytic hydrogenation of acyl phosphonates was utilized in the dynamic kinetic resolution of α-aryl acyl phosphonates, providing β-stereogenic α-hydroxy phosphonic acid derivatives.

An Overview of Stereoselective Synthesis of α-Aminophosphonic Acids and Derivatives

An overview of all methodologies published during the last few years focused to the stereoselective (diastereoselective or enantioselective) synthesis of α-aminophosphonic acids and derivatives is reported. The procedures have been classified according a retrosynthetic strategy and taking into account the formation of each one of the bonds connected to the chiral centre.

Organocatalytic enantioselective synthesis of alpha-hydroxy phosphonates

Tertiary alpha-hydroxy phosphonates have been synthesized in good yields and high enantiomeric purity (up to 99% ee) through a novel l-proline-catalyzed cross aldol reaction of alpha-keto phosphonates and ketones.

Organocatalytic highly enantioselective synthesis of secondary alpha-hydroxyphosphonates

[reaction: see text] The first organocatalytic cross aldol reaction of ketones and diethyl formylphosphonate hydrate has been realized by using readily available l-prolinamide as the catalyst. Secondary alpha-hydroxyphosphonates have been synthesized in high enantioselective (up to >99% ee) and good diastereoselectivity.

The Assignment of the Absolute Configuration of Diethyl Hydroxy- and Aminophosphonates by 1H and 31P NMR Using Naproxen as a Reliable Chiral Derivatizing Agent

The assignment of the absolute configuration of hydroxy- and aminophosphonates by their double derivatization with commercially available naproxen is presented. The correlation between the spatial arrangement around the stereogenic carbon center and the signs of the DeltadeltaRS allows determination of the absolute configuration of hydroxy- and aminophosphonates by simple comparison of the 1H and 31P NMR spectra of the (R)- and (S)-naproxen ester or amide derivatives. Extensive conformational analysis (theoretical calculations, low-temperature experiments) supported by the NMR studies of structurally diverse naproxen esters and amides of hydroxy- and aminophosphonates proved that a simplified model can be successfully used.

Enantiodifferentiation of N-benzyloxycarbonylaminophosphonic and phosphinic acids and their esters using cyclodextrins by means of capillary electrophoresis

Capillary electrophoresis was successfully applied for separation of the enantiomers of N-benzyloxycarbonyl-alpha-aminophosphonic and alpha-aminophosphinic acids as well as their ethyl and phenyl monoesters with the use of a range of commercially available cyclodextrins (alpha, beta and hydroxypropyl-gamma-cyclodextrins) as chiral selectors. The dependence of effectiveness of separation on type and concentration of these chiral selectors as well as on pH of background electrolyte was examined in some detail.

[Synthesis of phosphonic acid and phosphinic acid derivatives for development of biologically active compounds]

This paper covers recent publications from our laboratory on the synthesis of a variety of phosphonate and phosphinate derivatives. New methods for the enantioselective synthesis of alpha-hydroxyphosphonates were established by Lewis acid-mediated cleavage of homochiral 1,3-dioxaneacetals with P(OEt)(3) and chiral metal ligand-mediated hydrophosphonylation of aldehydes. Two diastereomers of HPmp derivatives were prepared by an application of these methods. The HPmp derivatives were convered to FPmp derivatives but with low diastereoselectivity. Hydrophosphonylation of alpha-aminoaldehydes afforded threo- and erythro-beta-amino-alpha-hydroxyphosphonates under chelation and nonchelation controlled conditions, respectively. The asymmetric dihydroxylation of alpha, beta-, and beta, gamma-unsaturated phosphonates with AD-mix-alpha and AD-mix-beta reagents gave alpha, beta- and beta, gamma-dihydroxyphosphonates with high enantioselectivity. The method was applied to the kinetic resolution of racemic alpha-oxygetated beta, gamma-unsaturated phosphonates. Treatment of allyloxymethylphosphonates with the base afforded alpha-hydroxyphosphonates via the [2,3]-Wittig reaction. Threo- and erythro-beta-amino-alpha-hydroxyphosphinates were obtained with high diastereoselectivity by phosphinylation of alpha-aminoaldehydes in the presence of (R)- and (S)-ALB, respectively. The phosphinylation of alpha-oxygenated aldehydes afforded the corresponding alpha, beta-dioxygenated phosphinates, but with low diastereoselectivity. Sphingomyelin analogues containing CF(2)PO(OH)(2) were synthesized starting from (S)- and (R)-Garner aldehyde for the purpose of obtaining potent sphyngomyelinase inhibitors. A useful method for the synthesis of alpha, alpha-difluorobenzylphosphonates was established based on the cross coupling reaction of an iodobenzene derivative with ZnCuBr(2)CF(2)PO(OEt)(2). The synthetic utility of ZnCuBr(2)CF(2)PO(OEt)(2) was examined to obtain alpha, alpha-difluoromethylenenphosphonates. The method was applied to a synthesis of PNP-inhibitory active compounds by combination of the purine base and alcohols containing difluoromethylenephosphonate. The methodology for the beta-selective N-glycosylation of 2,3-dideoxy glucoside was established by introducing phosphonothioates at the 3-position of glycosyl doners instead of phosphonate. Synthesis of new acylic nucleotide analogues designed based on the structural modification of ARS2267 is also described. Finally, kiral synthesis of some phosphonates was achieved using lipase through kinetic resolution.

Stereoselective synthesis of phosphoramidate alpha(2-6)sialyltransferase transition-state analogue inhibitors

The asymmetric synthesis of novel, potent phosphoramidate alpha(2-6)sialyltransferase transition-state analogue inhibitors such as (R)-9 (K(i)=68 microM) is described, via condensation of cytidine phosphitamide 6 with key chiral, non-racemic alpha-aminophosphonates, prepared in >98% ee by Mitsunobu azidation followed by Staudinger reduction of the corresponding chiral, non-racemic alpha-hydroxyphosphonates.