Diol moiety

Macrolides containing only neutral sugars were obtained from a platenomycin-producing organism (217,218). Four demycarosyl derivatives of platenomycins were isolated from biosyntheticaHy blocked mutants of S. platensis, two of these possessed a methyl group rather than an aldehyde (219). A pair of novel compounds related to carbomycin were isolated in which one contained an unusual 10,ll-dihydro-12,13-diol moiety, the other a 14-hydroxy-epoxyenone moiety (220). 

In the Mukaiyama variation of the aldol reaction, 3-benzoyloxy-2-trimethylsiloxy-l-butene adds to 2-methylpropanal in a stereoselective manner. Best results are obtained in the presence of titanium(IV) chloride, giving the adducts 9/10 in a diastereomeric ratio of 92 8. Hydrolysis of the benzoyl group and subsequent oxidative cleavage of the 1,2-diol moiety liberates / -hy-droxycarboxylic acids593. 

Chiral crown ethers possessing two chiral cw-l-phenylcyclohexane-l,2-diol moieties as well as a p-(2,4-dinitrophenylazo)phenol chromophore were prepared and with chiral alkylamines were observed to show enantiomeric selectivity <96JCS(P1)383>. 

Boro nophenyl) alanine (BPA) is a practical boron compound which is clinically used for the treatment of not only malignant melanoma but also of brain tumors, in neutron capture therapy (Scheme 1-40) [105, 152, 153]. Although (pinacolato)di-boron (82) is an excellent reagent to afford the corresponding boronate in 88% yield, it strongly resists the hydrolysis to arylboronic acids. Alternatively, the 1,3-diphenyl-propanediol ester (85) is more convenient to deprotect the diol moiety by catalytic hydrogenolysis [105]. 

D-fructose (4370 M"1) > D-galactose (276 M"1) > D-glucose (110 M"1). From these results, it was confirmed that the PMBV/PVA hydrogel was formed under biological conditions, and that the reversible properties of the hydrogel corresponded to the formation of a complex between the phenylboronic acid group in PMBV and the diol moiety in PVA. 

All one-bond H- C connectivities were established by a heteronuclear multiple-quantum coherence (HMQC) experiment. Partial structures including a tetraene system, a phenyl group and a diol moiety as shown in Figure 27A were determined by a COSY experiment. 

These results point to a significant effect of the configuration of the diol moiety on the intracomplex forces involved in the isomeric [C/j-M/j/j], [C/j-M/js], and [C/j-Mss] adducts. The OH- - -O hydrogen bonding in these complexes is responsible for the bathochromic shifts observed in the corresponding spectra. " Different spectral shifts for diastereomeric complexes are often due to the superimposing effects of attractive dispersive (polarization) and repulsive (steric) interactions. ... 

Although the presence of BINOL in the ligands so far discussed has shown itself to be particular effective, modification of the diol moiety provides new classes of ligands for this addition reaction. Alexakis, screening a number of chiral phosphites in the Cu(OTf)2-catalyzed 1,4-addition, showed that an ee of 40% could be obtained for the addition of Et2Zn to 2-cyclohexenone and of 65% for addition to chalcone, by using cyclic phosphites derived from diethyl tartrate [51]. 

Lycorine is the most abundant alkaloid in plants of the Amaryllidaceae. Several syntheses of racemic lycorine had been reported prior to our initiation of studies directed at an asymmetric synthesis of the unnatural enantiomer 64. 2 a common theme in all of the syntheses of ( )-lycorine has been the utilization of either an intermolecular or intramolecular Diels-Alder construction of the key C-ring of the alkaloid. This six-membered ring presents a rather formidable synthetic challenge because of the four contiguous stereogenic centers, the trans 1,2-diol moiety, and the juxtaposition of the aromatic substituent and the carbon-carbon double bond. 

Scheme 2.9 Mono-protection of symmetrical diol moieties.

Hydrolysis of Polyurethanes by Lipase. Effects of Mn of PCL-diol moiety on the hydrolysis of polyurethanes, which were composed of... 

The ternary systems, Cr(VI)/GSH/sugars, have been studied in detail by Kozlowski and coworkers.60 EPR signals were observed for the reactions of Cr(V) with biological reductants (such as GSH) in the presence of various sugars that possess 1,2-diol moieties [such as D-glucose (11) or D-ribose].72 Compound 11 is a probable candidate ligand responsible for Cr(V) coordination in the giso= 1.979 species in Cr (VI)-exposed animal tissues.19... 

In addition, the reduction of a-11 and (3-11 was s tudied in dimethyl sulfoxide as solvent, in the presence of pyridiniump-toluensulfonate. This medium makes mutarota-tion slower than the redox process.73 The two anomeric forms could reduce Cr(VI) and Cr(V) by formation of a Cr(VI) and Cr(V) ester intermediate. The equilibrium constant for this step and the rate of the redox step were different for each anomer for a-11, the equilibrium constant for ester formation is higher than for (3-11, but the redox process within this complex is faster for the latter anomer. These differences can be explained by the better chelating capacity of the 1,2-cri-diol moiety of a-11. Room-temperature CW-EPR spectra of these mixtures revealed for the a anomer several five-coordinated Cr(V)-bischelates (giso= 1.9820 [crilso 15.9xl(r4cm 1 (=47.7MHz)],... 

PCC transforms 5,6-dihydroxyalkenes into tetrahydrofurans in a highly stereoselective manner284 (see Equation below). This transformation can be explained by the initial formation of a cyclic chromate ester by reaction with the diol moiety, followed by an intramolecular oxidative addition of the chromate ester on the alkene. 

In this tetrol, a single secondary alcohol is oxidized with 88% yield thanks to the formation of the most stable cyclic stannylene intermediate by the regioselective reaction of BU2S11O with one of the 1,2-diol moieties in the molecule. 

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