Formal total synthesis of neopeltolide

A concise synthesis of the core structure of the macrolide neopeltolide was developed featuring a Prins cyclization to fashion the pyran ring. Key steps in the synthesis of aldehyde 16 were a Leighton allylation and a Feringa-Minnaard asymmetric methyl cuprate addition to an unsaturated thioester. For lactonization, a classical Yamaguchi macrolactonization was used. The longest linear sequence consists of 17 steps providing lactone 26 with an overall yield of 23%.     

On some numerical methods for an inverse potential problemin 2D semi infinite regions

We consider the inverse Dirichlet boundary value problem for the Laplace equation that consists in the reconstruction of the bounded inclusion in the 2D domain with infinite boundary from Cauchy data observed on it. In order to solve this problem we apply the Landweber [3] and hybrid [1] methods and investigate - mostly numerically - their goals and defects in the case of semi-infinite regions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Total synthesis and biological activity of neopeltolide and analogues

Combining the core structure of neopeltolide, lactone 16 a, with the oxazole-containing side chain 23 via a Mitsunobu reaction provided the cytotoxic natural product neopeltolide (2). The side chain 23 was prepared from oxazolone 24 via the corresponding triflate. Key steps in the preparation of 23 were a Sonogashira coupling, an enamine alkylation, and a Still-Gennari Horner-Emmons reaction. By changing the Leighton reagent in the allylation step, the 11-epimer of lactone 16 a, compound 50 was prepared. This led to 11-epi-neopeltolide 51. The 5-epimer of neopeltolide, compound 52, could be obtained from the minor isomer of the Prins cyclization. Furthermore, a range of analogues with modifications in the side chain were prepared. All derivatives were checked for toxicity effects on mammalian cell cultures and inhibitory effects on NADH oxidation in submitochondrial particles of bovine heart. Modifications in the lactone part are tolerated to some degree. On the other hand, shortening the distance between the oxazole and the lactone causes a significant drop in activity. Analogue 65 with an additional double bond is equally or even more active than neopeltolide itself.     

Synthesis of the core structure of cruentaren A

The core structure of the macrolactone cruentaren A (1) was prepared via a ring-closing alkyne metathesis reaction. The corresponding ester 33 was constructed from the benzoic acid derivative 14 and the diol 30. As a key step in the synthesis of acid 14, an aldol reaction resulted in the required anti-OH/Me pattern. The anti-configuration in the stereotetrad of diol 30 was established by a Marshall reaction. [reaction: see text].     

Synthesis and biological evaluation of cruentaren A analogues

The complex macrolide cruentaren A is a highly selective and potent inhibitor of F-ATPase (F-type adenosine triphosphatase). As it shows some resemblance to benzolactone enamides like apicularen A, it was of interest to perform some structure-activity studies to delineate the key functional groups that are responsible for the activity. Building upon our previously developed route to cruentaren A, which is based on a ring-closing alkyne metathesis reaction (RCAM), several cruentaren analogues were prepared. Replacement of the 3-hydroxy hexanoic part with acids that lack the hydroxy group function resulted in a significant drop in cytotoxicity and F-ATPase inhibition. Furthermore, two enamide analogues 23 and 50 were synthesized. However, these compounds were only cytotoxic in the micromolar range. Under the conditions for cleavage of the C3 aromatic methyl ether, the enamide function was transformed to the corresponding oxazinanone, resulting in analogues 25 and 52.     

A Selective Pulse-Induction Metal Detector

Russian Physics Journal -