Preparation and evaluation of novel stationary phases for improved chromatographic purification of pneumocandin B0

Preparation and evaluation of a number of stationary phases for improved chromatographic purification of pneumocandin B0, a key intermediate in the synthesis of the antifungal agent, Cancidas, has led to the identification of several materials with potential for improved performance.     

Crystal engineering with heteroboranes. I. 1-Carboxy-1,2-dicarba-closo-dodecaborane(11)

The title compound, C₃H₁₂B₁₀O₂ or 1-COOH-1,2-closo-C₂B₁₀H₁₁, forms centrosymmetric dimers through intermolecular hydrogen bonding between the carboxylic acid groups, resulting in the formation of an eight-membered ring [R(8)]. The C=O bond of the carboxylic acid group almost eclipses the unsubstituted cage C atom, with a C—C—C—O torsion angle of 2.6 (2)°.     

Synthesis of an mRNA fragment of alanyl-tRNA synthetase gene in Escherichia coli using the 6-methyl-3-pyridyl group for protection of the imide functions of uridine and guanosine

The synthesis of 5'-GpGpUpGpU-3' is reported to demonstrate the synthetic use of the 6-methyl-3-pyridyl group for the protection of the O-4 and O-6 imide functions of uridine and guanosine, respectively. The 2'- and 5'-hydroxyl functions of the key intermediates were protected with two acid-labile groups: 3-methoxy-1,5-dicarbomethoxypentane-3-yl (MDMP) and 9-(4-octadecyloxyphenyl)xanthen-9-yl (C18Px), respectively. The internucleotide phosphotriesters were protected with 2-chlorophenyl and the 9-fluorenylmethyl group was employed for 3'-terminal phosphate protection.