Isolation and characterization of side-products formed through ∆2-isomerization in the synthesis of cefpodoxime proxetil.

In the synthesis of cephalosporin antibiotics, esterified in 4-position, the ∆2-isomerization is a well-known side reaction proceeding under basic conditions. In this work, we investigated the ∆2-isomerization of the esterified cefpodoxime proxetil. Due to the R-configuration and S-configuration of the stereogenic center in the side chain in 4-position, there are two starting materials being diastereomeric to each other.

Distinct expression of endothelin receptor subtypes A and B in luteinized human granulosa cells.

Endothelins (ET) are potent vasoconstrictive peptides originally isolated from vascular endothelial cells. Their biological effects are mediated through two different receptors, the endothelin-1 (ET-1)-selective endothelin receptor subtype ETA and the non-selective receptor subtype ETB. ET-1 protein has been found in human ovarian follicular fluid and ET-1 mRNA expression has been demonstrated in ovarian tissue.