Symbiotic schemes

Scheme 13 Istatin produced by symbiotic bacteria defends crustacean embryos from a pathogenic fungus...

In Scheme 1-71, the reversible reaction is shifted to the right when the anion, X, is larger and the cation, M+, is smaller. For example, this shift to the right is 100% in the presence of Na+, PI v, and only 35% in the presence of Na+, F (Hamon Astruc 1988). The equilibrium takes place as an exchange reaction between the two ion pairs. Reactions of this type are based on the symbiotic-effect premise The interaction between a hard cation and a hard anion or between two soft ions is stronger than that between two ions of different types. 

A partial and abbreviated scheme showing the interrelationship between the methane bacteria and other representatives of the anaerobic carbon cycle is listed in Figure 1. The heavy arrows indicate methane fermentations by individual species or perhaps in some cases by closely dependent symbiotes. The remaining reactions of Figure 1 are catalyzed by propionibacteria, clostridia, butyribacteria, and other anaerobes. The general references of Wood (13), Barker (4), and Stadtman (14) may be consulted for further details and additional fermentations. 

The mildest reagent for cleaving TBS ethers is pyridinium p-toluenesulfonate (PPTS) in a protic solvent — usually methanol. Under these conditions a primary TBS ether can be cleaved in the presence of a 2-(trimethylsilyl)ethoxy-methyl (SEM) ether and 2-(trimethylsilyl)ethyl ester [Scheme 4.26]. Primary TBS ethers cleave at room temperature but secondary TBS ethers may require elevated temperature. In the transformation shown in Scheme 4.27 two TBS ethers were cleaved in the presence of a TIPS ether." rerf-Butyldiphenylsilyl (TBDPS) ethers are impervious to attack under these conditions as evinced by the selective removal of a primary TBS ether in the presence of an equally exposed primary TBDPS ether in a synthesis of NodRm-IV factors, glycolipids produced by symbiotic fungi that elicit formation of nitrogen-fixing root nodules in legumes [Scheme 4.28]. ... 

Maier and Varseev recently applied MacMillan s elegant one-pot three-step protocol 115) (1. a-hydroxylation, 2. Horner-Wadsworth-Emmons HWE) olefination, 3. N—O cleavage) for the conversion of the (5)-citronellol-derived aldehyde 132 to y-hydroxy-a,p-unsaturated ester 133 early in their 18-step first total synthesis of neosymbioimine (134) 116), a minor amphoteric metabolite of the symbiotic marine dinofiagellate Symbiodinium sp. 117) (Scheme 31). 

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