HATU

Novel primaquine (PQ) and halogenaniline asymmetric fumardiamides ;4a;⁻;f;, potential Michael acceptors, and their reduced analogues succindiamides ;5a;⁻;f; were prepared by simple three-step reactions: coupling reaction between PQ and mono-ethyl fumarate (;1a;) or mono-methyl succinate (;1b;), hydrolysis of PQ-dicarboxylic acid mono-ester conjugates ;2a;,;b; to corresponding acids ;3a;,;b;, and a coupling reaction with halogenanilines. 1-[bis(Dimethylamino)methylene]-1;H;-1,2,3-triazolo[4,5-;b;]pyridinium 3-oxide hexafluorophosphate (HATU) was used as a coupling reagent along with Hünig's base. Compounds ;4; and ;5; were evaluated against a panel of bacteria, several ;Mycobacterium; strains, fungi, a set of viruses, and nine different human tumor cell lines. ;p;-Chlorofumardiamide ;4d; showed significant activity against ;Staphylococcus aureus,;Streptococcus pneumoniae; and ;Acinetobacter baumannii;, but also against ;Candida albicans; (minimum inhibitory concentration (MIC) 6.1⁻12.5 µg/mL). Together with ;p;-fluoro and ;p;-CF₃ fumardiamides ;4b;,;f;, compound ;4d; showed activity against ;Mycobacterium marinum; and ;4b;,;f; against ;M. tuberculosis;. In biofilm eradication assay, most of the bacteria, particularly ;S.

The preparation of sterically hindered and polyfunctional C(alpha,alpha)-disubstituted alpha-amino acids (alpha alpha AAs) via alkylation of ethyl nitroacetate and transformation into derivatives ready for incorporation into peptides are described. Treatment of ethyl nitroacetate with N,N-diisopropylethylamine (DIEA) in the presence of a catalytic amount of tetraalkylammonium salt, followed by the addition of an activated alkyl halide or Michael acceptor, gives the doubly C-alkylated product in good to excellent yields. Selective nitro reduction with Zn in acetic acid or hydrogen over Raney Ni gives the corresponding amino ester that, upon saponification, can be protected with the fluorenylmethyloxycarbonyl (Fmoc) group. The first synthesis of an orthogonally protected, tetrafunctional C(alpha,alpha)-disubstituted analogue of aspartic acid, 2,2-bis(tert-butylcarboxymethyl)glycine (Bcmg), is described. Also, the sterically demanding C(alpha,alpha)-dibenzylglycine (Dbg) has been incorporated into a peptide using solid-phase synthesis. It was found that once sterically congested Dbg is at the peptide N-terminus, further chain extension becomes very difficult using uronium or phosphonium salts (PyAOP, PyAOP/HOAt, HATU).

More than one oligonucleotide can be synthesized at a time by linking multiple oligonucleotides end-to-end in a tandem manner on the surface of a solid-phase support. The 5'-terminal hydroxyl position of one oligonucleotide serves as the starting point for the next oligonucleotide synthesis. The two oligonucleotides are linked via a cleavable 3'-O-hydroquinone-O,O'-diacetic acid linker arm (Q-linker). The Q-linker is rapidly and efficiently coupled to the 5'-OH position of immobilized oligonucleotides using HATU, HBTU, or HCTU in the presence of 1 equiv of DMAP. This protocol avoids introduction of phosphate linkages on either the 3'- or 5'-end of oligonucleotides. A single NH(4)OH cleavage step can simultaneously release the products from the surface of the support and each other to produce free 5'- and 3'-hydroxyl termini. Selective cleavage of one oligonucleotide out of two sequences has also been accomplished via a combination of succinyl and Q-linker linker arms. Tandem synthesis of multiple oligonucleotides is useful for producing sets of primers for PCR, DNA sequencing, and other diagnostic applications as well as double-stranded oligonucleotides. Tandem synthesis of the same sequence multiple times increases the yield of material from any single synthesis column for maximum economy in large-scale synthesis.