The first facile and efficient Zn(OTf)2-catalyzed direct coupling of unprotected propargylic alcohols with arylphosphine oxides has been developed, affording a general, one-step approach to access structurally diverse γ-ketophosphine oxides via sequential Meyer–Schuster rearrangement/phospha-Michael reaction along with new C(sp3)—P and C═O bond formations, operational simplicity, and complete atom economy under ligand-free and base-free conditions.

•A novel stable isotope labeling strategy based on organic phosphorus chemistry is introduced.•The chiral metabolites could be converted to diastereomers and separated on C18 reversed-phase column.•The ionization efficiency in ESI processes and chromatographic separations of hydrophilic metabolites are improved.•The chirality of labeled enantiomers can be determined by using different detectors such as 31P NMR, UV, and MS.•The practical applicability is investigated for quantitative profiling of amine-containing metabolites in urine.Stable isotope chemical labeling liquid chromatography-mass spectrometry (LC-MS) is a powerful strategy for comprehensive metabolomics profiling, which can improve metabolites coverage and quantitative information for exploration of metabolic regulation in complex biological systems. In the current work, a novel stable isotope N-phosphoryl amino acids labeling strategy (SIPAL) has been successful developed for quantitative profiling of amine-containing metabolites in urine based on organic phosphorus chemistry. Two isotopic reagents, 16O2- and 18O2-N-diisopropyl phosphoryl l-alanine N-hydroxysuccinimide esters (16O/18O-DIPP-L-Ala-NHS), were firstly synthesized in high yields for labeling the amine-containing metabolites. The performance of SIPAL strategy was tested by analyzing standard samples including 20 l-amino acids, 10 d-amino acids and small peptides by using LC-MS. We observed highly efficient and selective labeling for SIPAL strategy within 15 min in a one-pot derivatization reaction under aqueous reaction conditions. The introduction of a neutral phosphate group at N-terminus can increase the proton affinity and overall hydrophobicity of targeted metabolites, leading to the better ionization efficiency in electrospray ionization processes and chromatographic separations of hydrophilic metabolites on reversed-phase column. Furthermore, the chiral metabolites, such as d-amino acids, could be converted to diastereomers after SIPAL and successfully separated on regular reversed-phase column. The chirality of labeled enantiomers can be determined by using different detection methods such as 31P NMR, UV, and MS, demonstrating the potential application of SIPAL strategy. In addition, absolute quantification of chiral metabolites in biological samples can be easily achieved by using SIPAL strategy. For this purpose, urine samples collected from a healthy volunteer were analyzed by using LC-ESI-Orbitrap MS. Over 300 pairs of different amine-containing metabolites have been manually identified with high relative abundance (signal-to-noise ratios greater than 10). Finally, a standard peptide could be relatively quantified by using SIPAL strategy in combination with MALDI-TOF MS, suggesting the potential application of this strategy for quantitative proteomics.Download high-res image (212KB)Download full-size image

A novel and efficient nickel-catalyzed tandem 1,4-1,2-addition of P(O)H compounds to 1,10-phenanthrolines forming various 2,4-diphosphono-1,2,3,4-tetrahydro-1,10-phenanthrolines has been developed. This reaction breaks up the aromatic stabilization and directly introduces two phosphorus moieties in one single step. This finding is the first example of transition-metal-catalyzed double hydrophosphonylation of 1,10-phenanthrolines.

The first example of Pd-catalyzed Suzuki cross-coupling of readily available arylhydrazines with arylboronic acids via C–N bond cleavage was developed under air, affording various biaryl compounds with broad substrate applicability and moderate to good yields. Moreover, the rigorous exclusion of air/moisture is not required in these transformations. Thus, the protocol represents a simple and efficient procedure to access biaryl compounds.

The nucleoside-based antiviral phosphoramidates and H-phosphonates were synthesized and separated using reversed-phase liquid chromatography on bridged ethane hybrid (BEH) C18 column packed with 1.7 μm particles of non-chiral stationary phase. The influences of the composition of mobile phase and column temperature have been investigated to optimize the diastereoisomeric separation. Complete separations of the phosphoramidate and H-phosphonate prodrugs with good resolution (RS = 1.99–2.77) were achieved within a short time (5–9 min). The validation study of the optimized method including linearity, accuracy, repeatability and detection limit has revealed it is better performance versus conventional HPLC method. In addition, HPLC was combined with high resolution electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS), which enabled the exact mass measurement and high sensitivity. Using MS as detection, the limits of detection and limits of quantification of the studied pronucleotide diastereoisomers were determined in the range of several nmol L−1 level.

Cationic metal ion-coordinated N-diisopropyloxyphosphoryl dipeptides (DIPP-dipeptides) were analyzed by electrospray ionization multistage tandem mass spectrometry (ESI-MSn). Two novel rearrangement reactions with hydroxyl oxygen or carbonyl oxygen migrations were observed in ESI-MS/MS of the metallic adducts of DIPP-dipeptides, but not for the corresponding protonated DIPP-dipeptides. The possible oxygen migration mechanisms were elucidated through a combination of MS/MS experiments, isotope (18O, 15N, and 2H) labeling, accurate mass measurements, and density functional theory (DFT) calculations at the B3LYP/6-31 G(d) level. It was found that lithium and sodium cations catalyze the carbonyl oxygen migration more efficiently than does potassium and participation through a cyclic phosphoryl intermediate. In addition, dipeptides having a C-terminal hydroxyl or aromatic amino acid residue show a more favorable rearrangement through carbonyl oxygen migration, which may be due to metal cation stabilization by the donation of lone pair of the hydroxyl oxygen or aromatic π-electrons of the C-terminal amino acid residue, respectively. It was further shown that the metal ions, namely lithium, sodium, and potassium cations, could play a novel directing role for the migration of hydroxyl or carbonyl oxygen in the gas phase. This discovery suggests that interactions between phosphorylated biomolecules and proteins might involve the assistance of metal ions to coordinate the phosphoryl oxygen and protein side chains to achieve molecular recognition.