Extension ladder: The successful application of epoxide-opening strategies towards the synthesis of ladder-type polyethers is contingent upon further elaboration of the product. By employing two different functionalized templates, a fragment of gymnocin A that bears four sites for subsequent fragment coupling has been prepared (see scheme; Bn = benzyl).

The polyether antibiotics reported by the year 1968 were nigericin1) (X-4642)), lasalocid (X-537A2)), X-2062), dianemycin3) and monensin4). Monensin (1) was the only one whose structure was known at that time. In the following decade, the number of distinct polyethers increased from these five to forty-six, almost all of which were structurally assigned. As a result of this rapid growth, a numb...

The red seaweed Laurencia viridis is a rich source of secondary metabolites derived from squalene. New polyethers, such as iubol (2), 22-hydroxy-15(28)- dehydrovenustatriol (3), 1,2-dehydropseudodehydrothyrsiferol (4), and secodehydrothyrsiferol (5) have been isolated and characterized from this alga. The structures were determined through the interpretation of NMR spectroscopic data and the re...

Potassium complexes are starting to gather more and interest from academia industry because of their intriguing application possibilities. Novel adducts potassium hexafluoroacetylacetonato [K(hfa)] with polyethers (monoglyme, diglyme, triglyme, tetraglyme) were synthesized through a single step reaction characterized FT-IR spectroscopy as well 1H 13C NMR spectroscopy. Single crystal X-ray diffr...

Part III The Mobius Stnp Approach to Synthesis of Topologtcal Stereolsomers A Briuds and wreaths B The Mabms stnp approach 1 The THYME polyethers 2 Total synthesis of the first molecular MBbms stnp 3 Topology of the molecular MBbms stnp the MBbms ladders 4 Topological chlrahty of the MBbms ladder with three dtierentlated rungs 5 Breaking the rungs of a MGbms ladder C Synthesis of molecular knots

The ability of BT-SCF 3 and related 2-(fluoroalkylthio)benzothiazolium salts to activate tetrahydrofuran (THF) has been investigated. In the presence carboxylate nucleophiles, ring-opening polymerization reactions affording various fluorinated non-fluorinated polyethers are observed. Moreover, in absence a carboxylate, activation by benzothiazolium allows for α-deprotonation THF strong external...

Two novel squalene-derived triterpenes, spirodehydrovenustatriol (3) and 14-keto-dehydrothyrsiferol (4) were isolated from the red alga Laurencia viridis, together with two new and unusual C(17) terpenoids, adejen A (5) and B (6). These truncated structures possess structural similarities with other known squalene metabolites and their biogenetic origin has been proposed on the basis of an oxid...

Leishmanicidal drugs interacting stoichiometrically with parasite plasma membrane lipids, thus promoting permeability, have raised significant expectations for Leishmania chemotherapy due to their nil or very low induction of resistance. Inherent in this process is a decrease in intracellular ATP, either wasted by ionic pumps to restore membrane potential or directly leaked through larger membr...

AIM The aim of the present study is to compare the various elastomeric impression materials in terms of accuracy and dimensional stability, with respect to obtaining multiple casts from a single elastomeric impression at various times of pours. MATERIALS AND METHODS Three master dies were prepared for the impression making, two of these were made of brass containing a central hole with underc...