No abstract

Native and chemically derivatized proteins purified from serum and milk were assayed in vitro to assess their inhibiting capacity on the cytopathic effect of human immunodeficiency virus (HIV)-1 and human cytomegalovirus (HCMV) on MT4 cells and fibroblasts, respectively. Only native and conformationally intact lactoferrin from bovine or human milk, colostrum, or serum could completely block HCMV infection (IC50 = 35-100 micrograms/mL). Moreover, native lactoferrin also inhibited the HIV-1-induced cytopathic effect (IC50 = 40 micrograms/mL). When negatively charged groups were added to lactoferrin by succinylation, there was a 4-fold stronger antiviral effect on HIV-1, but the antiviral potency for HCMV infection was mostly decreased. Lactoferrin likely exerts its effect at the level of virus adsorption or penetration (or both), because after HCMV penetrated fibroblasts, the ongoing infection could not be further inhibited.

The first total synthesis of the antivirally active glycolipid cycloviracin B(1) (1) is described. The approach is based on a two-directional synthesis strategy which constructs the C(2)()-symmetrical macrodiolide core of the target by an efficient template-directed macrodilactonization reaction promoted by 2-chloro-1,3-dimethylimidazolinium chloride 14 as the activating agent. Attachment of the lateral fatty acid chains to the lactide core thus formed features not only one of the most advanced ligand-controlled addition reactions of a functionalized dialkyl zinc reagent to a polyfunctional aldehyde, but also a highly demanding Julia-Kocienski olefination of a tetrazolyl sulfone bearing electrophilic and base-labile beta-hydroxy ester motifs. By virtue of the flexibility of this synthesis plan, it was possible to prepare a series of macrodiolide cores differing only in the absolute stereochemistry at the branching points as well as a host of model compounds for the fatty acid appendices of cycloviracin. Comparison of these derivatives with the natural product allowed us to establish the as yet unknown absolute stereochemistry of 6 chiral centers of 1 as (3R,19S,25R,3'R,17'S,23'R). Thereby, the (13)C NMR shifts of the anomeric position of the beta-glycosides residing at those positions turned out to be excellent probes for the absolute configuration of the attached aglycones. The concise set of data thus obtained also makes clear that the proposed structure of the fattiviracins, a seemingly closely related family of glycoconjugates, is not matched by the published data. Finally, the biological activity of synthetic 1 and some of the key intermediates obtained en route to this natural product was investigated, showing that the entire construct is necessary for appreciable and selective antiviral activity.