Diols esters

Fig. 5 Presentation of the 3D organisation of the RG-II dimer in which two apioses are cross-linked by a 1 2 borate-diol ester, as proposed by Perez et al. [23]...

Interestingly, okadaic acid diol ester (16) in the culture medium is oxidatively transformed into the more hydrophilic metabolites 18-20 by intact cells of the diatom Thalassiosira weissflogii [52,53]. This transformation is speculated to change the toxic metabolite with allelopathic activity into a less toxic transport form that can be better excreted by the diatom. 

Scheme 5 Release of okadaic acid (17) from less toxic precursors by E. lima (left). Oxidative transformation of okadaic acid diol ester (16) by the diatom Thalassiosira weissflogii (right)...

E 475 Polyglycerol esters of fatty acids E 476 Polyglycerol polyricinoleate E 477 Propane-1,2-diol esters of fatty acids E 479b Thermally oxidised soya bean oil interacted with mono- and diglycerides of fatty acids E 481 Sodium stearoyl-2-lactylate... 

Emulsifier 477 Propan- 1.2-diol esters of fatty acids 25 7th Series 539, p 24, 1973... 

The corresponding syzz-isomer was, on the other hand, prepared from the potassium permanganate-mediated oxidation of trifluorocrotonate 10, derived from -hydroxy-butyrate. In this procedure, the diol ester with syn relative configuration was the only product detected. After acetylation, syn-11 was employed as a substrate for the enzymatic resolution affording both (2S,3S)-11... 

Preparation of optically active anti-diol ester (2S,3R)-9... 

Borate diol ester linkage between apiose rings in oligosaccharide clusters of rhamnogalacturonan II in two pectin chains. 

Diatoms also require boron, which is incorporated into the silicon-rich cell walls.3 Some strains of Streptomyces griseus produce boron-containing macrolide antibiotics such as aplasmomycin (right).0 Recently a function in plant cell walls has been identified (see also main text) as crosslinking of rhamnogalacturonan portions of pectin chains by borate diol ester linkages as illustrated. 

Write a balanced equation for reaction of boric acid (H3BO3) with two sugar rings to give a borate diol ester linkage (Box 20-E). 

This section outlines three chemical transformations designed to allow further synthetic elaboration of the diols obtained from AD. The first and most broadly applicable method is the conversion of the diols into cyclic sulfates, a functionality that has reactive properties like an epoxide but is even more electrophilic than an epoxide [68]. The second approach to diol activation is the regioselective conversion of one of the hydroxyl groups into a sulfonate ester [69], This approach requires that the diol be substituted in a way that leads to regioselective derivatization of one of the two hydroxyl groups, and diol esters are a prime example of such... 

Further residual metal oxides from catalysts used for polymer synthesis, e.g. poly-terephthalic acid diol ester, are oxides of antimony, gallium, germanium, cobalt, man-... 

Tertiary amines can serve as amine substrates for the boron-Mannich reaction, providing aromatic alkylation products of N,N-dialkyl-3-alkoxyanilines (Equation (125))573 and 1,3,5-alkoxy- or hydroxybenzenes (Equation (126)).574 The use of chiral diol esters of ( )-2-phenylethenylboronic acid for enantioselective alkylation resulted in 6-15% ee.575... 

Plants contain signiFcant concentrations of polysaccharides of which the potentially negatively charged oxygen functions can bind cations electrostatically or chelate them via polyhydroxy groups [89]. Particular attention was attracted by a structurally complex pectic polysaccharide rhamnogalacturonan-II (RG-II) [90]. This ubiquitous component of primary plant cell walls forms dimers cross-linked by 1 2 borate diol esters (dRG-II) that were found to complex in vitro sped be divalent cations and the majority of Ba, Pb, Sr, and rare earth elements (REEs) in fruit and vegetables [45, 91]. 

Physical properties are related to ester-segment structure and concentration in thermoplastic polyether-ester elastomers prepared hy melt transesterification of poly(tetra-methylene ether) glycol with various diols and aromatic diesters. Diols used were 1,4-benzenedimethanol, 1,4-cyclo-hexanedimethanol, and the linear, aliphatic a,m-diols from ethylene glycol to 1,10-decane-diol. Esters used were terephthalate, isophthalate, 4,4 -biphenyldicarboxylate, 2,6-naphthalenedicarboxylate, and m-terphenyl-4,4"-dicarboxyl-ate. Ester-segment structure was found to affect many copolymer properties including ease of synthesis, molecular weight obtained, crystallization rate, elastic recovery, and tensile and tear strengths. 

In addition to the use of a dialdehyde to react with 2 moles of Reissert compound in the synthesis of 25, terephthalaldehyde has been reacted with 19 and 20 to give the meso form and racemate of the bis diol esters.3 In the quinoline series the product has been converted to a compound having curariform activity. 

In plankton samples reach in Dinophysis acuta, the presence of a diol ester with a C8 chain was demonstrated in a sample from New Zealand (Suzuki et al. 2004). However, the alkaline lydrofysis methodology, which had led previously to suspecting the presence of esters in the New Zealand samples, did not show the presence of esters in D. fortii samples from Japan (Suzuki et al. 1999). In boiled samples of D. acuminata and D. acuta harvested in Portugal, and D. acuminata harvested in... 

Figure. 12.5. Biotransformation of DSP toxins diol esters from Dinophysis are enzymatically hydrolyzed by the algae esterase and later acylated in shellfish digestive glands.

---