Conformational differences between O- and C-glycosides: the alpha-O-man-(1-->1)-beta-Gal/alpha-C-Man-(1-->1)-beta-Gal case--a decisive demonstration of the importance of the exo-anomeric effect on the conformation of glycosides

The conformational behavior of alpha-O-Man-(1-->1)-beta-Gal (1) and its C-analogue (2) has been studied using J/NOE NMR data, molecular mechanics, molecular dynamics, and ab initio calculations. The population distribution around the glycosidic linkages of 1 and 2 is rather different, especially for the alpha-Man linkage. A lower limit for the exo-anomeric effect in water has been experimentally determined.     

Synthesis of the non-classical acetogenin mucocin: a modular approach based on olefinic coupling reactions

A three component modular synthesis of the potent antitumor agent mucocin, based on olefinic coupling reactions, is described. A cross-metathesis on tetrahydropyran and tetrahydrofuran alkene components was used to assemble a stereochemically complex, non-adjacently-linked bicyclic ether. The latter was elaborated to a sulfone and partnered with a butenolide aldehyde component in a Julia-Kocienski olefination to provide the mucocin framework, which was converted to the natural product after hydrogenation and alcohol deprotection.     

A convergent strategy for the synthesis of beta-carba-galacto-disaccharides

[reaction in text] A convergent strategy for the synthesis of beta-carba-galacto-disaccharides is illustrated by the preparation of 1 and 4, from a central "glycone" component 22, and the corresponding "aglycone" segments, monosaccharide alcohols, 23a or 23b. The key step is the formation of the carbasugar ring via an oxocarbenium ion-enol ether cyclization.     

Visual spatial memory is enhanced in female rats (but inhibited in males) by dietary soy phytoestrogens

Background  

In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen). This study examined the influence of phytoestrogens (estrogen-like plant compounds) on VSM, utilizing radial arm-maze methods to examine varying aspects of memory. Additionally, brain phytoestrogen, calbindin (CALB), and cyclooxygenase-2 (COX-2) levels were determined.     

An iodoetherification-dehydroiodination strategy for the synthesis of complex spiroketals from dihydroxyalkene precursors

Dihydroxyalkenes or their monoprotected alcohol derivatives are transformed to 5,5- and 5,6-spiroketals through a sequence involving an initial iodocyclization, followed by a silver triflate mediated spiroketalization step on the derived hydroxy-iodoether.     

Synthesis of beta-C-galacto-pyranosides with fluorine on the pseudoanomeric substituent

[reaction: see text] beta-C-galacto-Pyranosides with CHF and CF2 substitutes for the glycosidic oxygen were prepared through a four-step sequence starting from a central 1-thio-1,2-O-isopropylidene acetal alcohol and different alpha-fluoro- and alpha,alpha-difluoro acids. The key step in the synthesis is the oxocarbenium cyclization of an intermediate enol ether-thioacetal to a C1-substituted glycal.     

Highly functionalized trans-2,5-disubstituted tetrahydrofurans from ribofuranoside templates: precursors to linked polycyclic ethers

Iodoetherification of C5 allylated ribo-furanosides leads to trans-2,5-disubstituted tetrahydrofurans with high selectivity. The application of this reaction to the synthesis of complex polycyclic ethers is illustrated in the preparation of a truncated, tricyclic analog of monensin A.     

Oxocarbenium ion cyclizations for C-branched cyclitols: synthesis of a relay intermediate for fumagillin analogues

A highly stereoselective oxocarbenium ion-alkene cyclization for synthesis of C-branched cylitols is described. This methodology was applied to 10S, a potentially versatile intermediate for side-chain analogues of the antiangiogenic agent fumagillin. Compound 10S was subsequently converted to diene 5. Because racemic 5 has been converted to racemic fumagillin, this synthesis of 5 constitutes a formal synthesis of the natural product.