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The cephalostatins. 21. Synthesis of bis-steroidal pyrazine rhamnosides (1).

ABSTRACT: The synthesis of bis-steroidal pyrazines derived from 3-oxo-11,21-dihydroxypregna-4,17(20)-diene (4) and glycosylation of a D-ring side chain with ?-L-rhamnose have been summarized. Rearrangement of steroidal pyrazine 10 to 14 was found to occur with boron triflouride etherate. Glycosylation of pyrazine 10 using 2,3,4-tri-O-acetyl-?-L-rhamnose iodide led to 1,2-orthoester-?-L-rhamnose pyrazine 17b. By use of a persilylated ?-L-rhamnose iodide as donor, formation of the orthoester was avoided. Bis-steroidal pyrazine 10 and rhamnosides 17b and 21c were found to significantly inhibit cancer cell growth in a murine and human cancer cell line panel. Pyrazine 9 inhibited growth of the nosocomial pathogen Enterococcus faecalis.

SUBMITTER: Pettit GR

PROVIDER: S-EPMC3251514 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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The cephalostatins. 21. Synthesis of bis-steroidal pyrazine rhamnosides (1).

Pettit George R GR Mendonça Ricardo F RF Knight John C JC Pettit Robin K RK

Journal of natural products 20110907 9

The synthesis of bis-steroidal pyrazines derived from 3-oxo-11,21-dihydroxypregna-4,17(20)-diene (4) and glycosylation of a D-ring side chain with α-L-rhamnose have been summarized. Rearrangement of steroidal pyrazine 10 to 14 was found to occur with boron triflouride etherate. Glycosylation of pyrazine 10 using 2,3,4-tri-O-acetyl-α-L-rhamnose iodide led to 1,2-orthoester-α-L-rhamnose pyrazine 17b. By use of a persilylated α-L-rhamnose iodide as donor, formation of the orthoester was avoided. Bi ...[more]

PMID: 21899266

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Crystal structure of di-aqua-bis-(2,6-di-methyl-pyrazine-?N)bis-(thio-cyanato-?N)cobalt(II) 2,5-di-methyl-pyrazine tris-olvate.

Project description:In the crystal structure of the title compound, [Co(NCS)2(C6H8N2)2(H2O)2]·3C6H8N2, the Co(II) cation is coordinated by two terminally N-bound thio-cyanate anions, two water mol-ecules and two 2,6-di-methyl-pyrazine ligands, forming a discrete complex with a slightly distorted octa-hedral N4O2 coordination environment. The asymmetric unit contains one Co(II) cation and three halves of 2,5-di-methyl-pyrazine solvate mol-ecules, all entities being completed by inversion symmetry, as well as one thio-cyanate anion, an aqua ligand and a 2,6-di-methyl-pyrazine ligand, all in general positions. In the crystal, discrete complexes are arranged in a way that cavities are formed where the noncoordinating 2,5-di-methyl-pyrazine mol-ecules are located. The coordination of the latter to the metal is prevented due to the bulky methyl groups in vicinal positions to the N atoms, leading to a preferential coordination through the 2,6-di-methyl-pyrazine ligands. The complex mol-ecules are linked by O-H?N hydrogen bonds between the water H atoms and the N atoms of 2,5-di-methyl-pyrazine solvent mol-ecules, leading to a layered structure extending parallel to (100).

| S-EPMC4719868 | biostudies-literature

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