Maciej Adamczyk

Methods for the conversion of isoxazolines to β-hydroxy ketones

Abstract Two methods have been developed for converting isoxazolines to β-hydroxy ketones in a stereospecific manner.

Collagen cross-links: Synthesis of pyridinoline, deoxypyridinoline and their analogues

Abstract An efficient chiral synthesis of (S,S)-(−)-3g, a key intermediate for the preparation of collagen cross-links pyridinoline (Pyd, 1) and deoxypyridinoline (Dpd, 2) was achieved from (4S)-5-(tert-butoxy)-4-[(tert-butoxycarbonyl)amino]-5-oxopentanoic acid (21b). Quaternization of (S,S)-(−)-3g with iodide (2S,5R)-(+)-4a followed by hydrolysis provided a first chiral synthesis of natural (+)-Pyd (1). 1-(2S)-(+)-Pyd (1) was also synthesized from (S,S)-(−)-3g and iodide (2S,5S)-(+)-4a. Similarly, quaternization of (S,S)-(−)-3g with iodide (2S)-(−)-4b, which was prepared from (2S)-(−)-6-amino-2-[(tert-butoxycarbonyl)amino]hexanoic acid (31) in three steps, followed by hydrolysis afforded natural (+)-Dpd (2) in 5.3% overall yield. Also, the synthesis of racemic Dpd [(±)-2] and a variety of its analogues is presented.

Circulating Cardiac Troponin-I Autoantibodies in Human Plasma and Serum

We identified IgG reactive with human cardiac troponin‐I (cTnI) in plasma and serum samples (N= 1930) from normal blood donors, and in sample cohorts characterized on the basis of clinical biomarkers associated with cardiac, infectious, and autoimmune diseases. cTnI and brain natriuretic peptide were the biomarkers chosen to reflect myocyte damage or left ventricular dysfunction, respectively. The infectious disease cohorts were serologically positive for antibodies to hepatitis B (natural infection), hepatitis C virus, and Chagas (i.e., T.cruzi). The autoimmune cohorts were represented by samples from diagnosed systemic lupus erythematosus (biomarker: dsDNA) and rheumatoid arthritis (biomarker: rheumatoid factor) subjects. The prevalence of IgG autoantibodies reactive with cTnI was high in the normal donor cohort (95/750, 12.7%). The prevalence in the other sample cohorts was not significantly different from that in the normal blood donors, with the exception of a slight increase in the rheumatoid factor cohort (28/137, 20.4%). The presence of anti‐cTnI IgG in highly reactive samples was confirmed by inhibition with the antigen and further by screening with a library of peptides derived from the human cTnI amino acid sequence. Our data suggest that these autoantibodies are polyspecific, encompassing epitopes across the entire cTnI sequence, including the cardiac‐specific amino terminal region.

Papain digestion of different mouse IgG subclasses as studied by electrospray mass spectrometry

On-line liquid chromatography-electrospray ionization mass spectrometry (LC/ESI-MS) has been utilized to monitor the papain digestion of mouse monoclonal antibodies (mAb) of different subclasses (IgG1, IgG2a, IgG2b, and IgG3). The method is simple, rapid, sensitive, and allows for simultaneous determination of digestion products and the identification of microheterogenous fragments. The results provide important insight into the mechanism of papain digestion of mouse IgGs of different subclasses.

An easy preparation of hapten active esters via solid supported EDAC

Abstract Bioconjugates are preferably prepared by reacting an active ester of the hapten of interest to the protein. Preparation of active esters with solid supported EDAC and N -hydroxysuccinunide or pentafluorophenol affords active esters in excellent yield and purity

Preparation and use ofN-hydroxysuccinimidyl active ester resins

Abstract Syntheses of solid-phase active esters derived from new N-hydroxysuccinimidyl resins 5a and 5b are described. Their practical utility is illustrated in the ready formation of amides in high yield and high purity.

Novel 7-hydroxycoumarin based fluorescent labels

Abstract Five new 7-hydroxy-8-(N-alkylaminomethyl)coumarin labels ( 6a-e ) were prepared from 4-(4-carboxybutyl)-7-hydroxycoumarin ( 4 ) in 28–48% yield. Compared to 4-methylumbelliferone (4-MU, 1 ), the new fluorescent labels exhibited higher emission intensity over a broader pH range. Extinction coefficients, quantum yields and pKa values are also reported for these labels.

TOTAL SYNTHESIS OF (+)-DEOXYPYRROLOLINE : A POTENTIAL BIOCHEMICAL MARKER FOR DIAGNOSIS OF OSTEOPOROSIS

The collagen cross-link (+)-deoxypyrrololine (Dpl, 1), a potential biochemical marker for diagnosis of osteoporosis, has been obtained by a general and convergent total synthesis. The key synthetic features involve utilization of a L-glutamic acid derivative as a source for all three chiral centers in (+)-1, and construction of the pyrrole ring by condensation of an alpha-acetoxynitro compound with benzyl isocyanoacetate.

Charge derivatization of peptides to simplify their sequencing with an ion trap mass spectrometer.

The low energy collision-induced dissociation of fixed-charge derivatives [tris(2,4,6-trimethoxyphenyl)phosphonium] of peptides was investigated using an electrospray ion trap mass spectrometer. The fixed charge directed the fragmentation pattern and generated solely N-terminal fragments with minimal internal rearrangement, regardless of the presence and position of basic amino acids in the peptide chain. Generally only b-type ions, accompanied by less intense a-type ions, were observed, depending on the collision energy. It was observed that the fixed charge controlled the fragmentation beyond typical MS/MS, and thus the capacity of the ion trap to perform multiple stage fragmentation (MS(n)) was found particularly useful for obtaining the complete sequence information of the peptides.

Lipase mediated hydrolysis of rapamycin 42-hemisuccinate benzyl and methyl esters

Abstract Benzyl and methyl esters of rapamycin 42-hemisuccinate were hydrolyzed under very mild conditions to the rapamycin hemisuccinate using lipase from Pseudomonas sp . This selective deprotection was performed on a ≥100 mg scale for both esters resulting in 50% isolated yield from the methyl ester and 29% from the benzyl ester of the desired acid.