David R. Lieberman

Synthesis of the 5-HT1D receptor agonist MK-0462 via a Pd-catalyzed coupling reaction

Abstract Application of a palladium-catalyzed coupling between 3 and 5a to the synthesis of the novel 5-HT 1D receptor agonist MK-0462 ( 1 ), a potential anti-migraine drug, is described.

Catalytic, Asymmetric, and Stereodivergent Synthesis of Non-Symmetric β,β-Diaryl-α-Amino Acids

We report a concise, enantio- and diastereoselective route to novel nonsymmetrically substituted N-protected β,β-diaryl-α-amino acids and esters, through the asymmetric hydrogenation of tetrasubstituted olefins, some of the most challenging examples in the field. Stereoselective generation of an E- or Z-enol tosylate, when combined with stereoretentive Suzuki-Miyaura cross-coupling and enantioselective hydrogenation catalyzed by (NBD)2RhBF4 and a Josiphos ligand, allows for full control over the two vicinal stereogenic centers. High yields and excellent enantioselectivities (up to 99% ee) were obtained for a variety of N-acetyl, N-methoxycarbonyl, and N-Boc β,β-diaryldehydroamino acids, containing a diverse and previously unreported series of heterocyclic and aryl substituted groups (24 examples) and allowing access to all four stereoisomers of these valuable building blocks.

Synthesis of Vaniprevir (MK-7009): Lactamization To Prepare a 22-Membered Macrocycle

Development of a practical synthesis of MK-7009, a 20-membered [corrected] macrocycle, is described. A variety of ring-closing strategies were evaluated, including ring-closing metathesis, intermolecular palladium-catalyzed cross-couplings, and macrolactamization. Ring closure via macrolactamization was found to give the highest yields under relatively high reaction concentrations. Optimization of the ring formation step and the synthesis of key intermediates en route to MK-7009 are reported.

Employment of on-line FT-IR spectroscopy to monitor the deprotection of a 9-fluorenylmethyl protected carboxylic acid peptide conjugate of doxorubicin

A method for accurately determining the end-point, >98% conversion, of the deprotection reaction of a highly toxic 9-fluorenylmethyl (Fm) ester 1b to its corresponding carboxylate 1d in real time by FT-IR spectroscopy is reported. Advantages of this method over analysis by conventional chromatographic means include real time determination of the end-point of a reaction that is time sensitive to by-product formation, and elimination of sampling a highly toxic reaction mixture. The FT-IR method is based on monitoring, in real time, the disappearance of the Fm ester carbonyl band for 1b at 1737 cm(-1), during deprotection by piperidine, and calibration models were established by Partial Least Squares (PLS) regression analysis with high performance liquid chromatography (HPLC) as reference. The best calibration model was built with 5 PLS factors in the spectral range of 1780-1730 and 1551-1441 cm(-1) and resulted in a standard error of cross validation (SECV) of 0.63 mM 1b and a standard error of prediction (SEP) of 0.51 mM 1b in the range of 0-25 mM. This error of prediction is approximately 0.8% of the initial concentration of 1b and is well within our specifications of <2% initial concentration.

An Efficient Synthesis of the Indole Acetic Acid Metabolite of MK-0462

Abstract A palladium-catalyzed coupling of iodoaniline 2 with bis-TES propargyl alcohol 3 gives indole-3-methanol 4b in 72% yield. Displacement of the hydroxy group of 4b by sodium cyanide followed by hydrolysis of the cyano group and desilylation provides the indole acetic acid metabolite, L-749,335 (1), of the 5-HT1D receptor agonist MK-0462.