Diols s. a. Dihydroxy

It displays a somewhat complementary substrate specificity to HLADH. While HLADH oxidizes meso-diols with secondary hydroxyl groups rather badly, they are readily oxidized by GDH to the corresponding (S)-a-hydroxyketones l L Furthermore, the natural substrate glycerol is transformed to achiral dihydroxy acetone by GDH while HLADH produces optically active (S)-glyceraldehyde. In many cases GDH seems to prefer secondary hydroxyl groups (Table 16.2-5), although this rule of thumb has some exceptions. 

During the 1960 s, the above sequence of reactions was confirmed by different in vitro studies. Mendelsohn and Staple showed that labelled cholesterol could be converted into 5j8-cholestane-3a,7a,12 -triol by 20000 X g supernatant fluid of rat liver homogenates [23]. The enzymatic conversion of cholesterol into 7a-hydroxy-cholesterol was first shown by Danielsson and Einarsson using the microsomal fraction fortified with NADPH [24]. The conversion of 7 -hydroxycholesterol into 7 -hydroxy-4-cholesten-3-one was found to be catalysed by the microsomal fraction fortified with NAD [25]. The latter steroid was converted into 7a,12a-dihydroxy-4-cholesten-3-one by the microsomal fraction and NADPH [26]. The conversion of 7 -hydroxy-4-cholesten-3-one and 7a,12a-dihydroxy-4-cholesten-3-one into the corresponding 3a-hydroxy-5/8-saturated steroids was catalysed by soluble NADPH-de-pendent enzymes [25,27,28]. Since Hutton and Boyd found that 4-cholestene-3 ,7 -diol was a product of 7a-hydroxy-4-cholesten-3-one in vitro [25], it was first... 

Other precursors of the muricholates via 6)8-hydroxylation include 5)8-cholanic acid [78], lithocholic acid [84-86], 7-oxolithocholic acid [95,96], and ursodeoxycholic acid (3a,7j6-dihydroxy-5/3-cholanic acid) [97], The rat metabolized 12a-hydroxy-5/S-cholanic acid to 6/S,12a-dihydroxy-5)S-cholanic acid [83] and a small amount of 6)3,7a,12a-trihydroxy-5 -cholanic acid [98]. 3a,6)8,12a-Trihydroxy-5)8-cholanic acid was isolated from urine of surgically jaundiced rats after administration of de-oxycholate [99]. A series of bile acids from rat bile of unconfirmed structures but containing the 6/3,7/3-diol will be reviewed in Section II1.3. 

In the same way, El Pray and Slonecki [22] prepared (polyether-6-polyester)s by polycondensation of a diol, an o ,a -dihydroxy-polyether, a dimerized fatty acid, and dimethyl terephthalate. 

Cerniglia CE, DT Gibson (1980a) Fungal oxidation of benzo[a]pyrene and (+/-)-fra s-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene evidence for the formation of a benzo[a]pyrene 7,8-diol-9,10-epoxide. J Biol Chem 255 5159-5163. 

In the consecutive hydrogenation of />,<5-diketo esters (Table 21.16), selection of the chiral ligand can determine the sense of diastereoselection, and the 3,5-syn dihydroxy product was formed predominantly upon use of a Ru-(S)-amino-phosphinephosphinite-((S)-AMPP) catalyst, although the enantioselectivity of the syn-product is poor (Table 21.16, entry 7) [103a]. Syn 3,5-diol formation... 

A 2 1 (- )-90-LAH reagent was employed in the asymmetric synthesis of a cij-diol (91) by reduction of c/j-2-acetoxy-6-phenylcyclohexanone (99,100). Diol 91 is of interest as the tetrahydro derivative of a metabolite obtained from the microbial oxidation of biphenyl. Diol 91 was obtained in 46% e.e. as determined by NMR in the presence of a chiral shift reagent. It was shown to have the absolute stereochemistry (lS,2/ )-dihydroxy-3(S)-phenylcyclohexane by oxidation to ( + )-2-(S)-phenyladipic acid of known absolute stereochemistry. 

For the manufacture of a transparent, tough, thermally stable polycarbonate, the bis(chloroformate)s of isosorbide and isomannide were copolymerized with such dihydroxy compounds as dihydroxybenzenes and aliphatic diols by using the interfacial condensation method.127... 

Endosulfan [115-29-7] (36) is the adduct of hexachlorocyclopentadiene and l,4-dihydroxy-2-butene which reacts subsequently with SOCl to produce 6>7>8>9>10>10-hexachloro-l,5,5, 6,9,9 -hexahydro-6>9-methano-2,4,3-benzodioxathiepin-3-oxide. The technical product is a brownish solid (mp 70— 100°C, vp 1.3 mPa at 30°C) which consists of about four parts of a-isomer (mp 108°C, cis with regard to the sulfite group) and one part of the p-isomer (mp 206°C, trans with regard to the sulfite group). The a-isomer, which is somewhat more insecticidal, is slowly converted to the more stable p-isomer at high temperature, and both isomers are oxidized slowly to endosulfan sulfate [1031-07-8] (mp 181°C). In acid media, both isomers form endosulfan diol [2157-19-9] (mp 203°C). The rat LDc-s are 43, 18 (oral) and 130, 74 (dermal) mg/kg. Endosulfan is a broad-spectrum insecticide for vegetables, fruits, and row crops. Unlike the other cyclodiene insecticides, it is biodegradable by hydrolysis at the sulfite ester bonds. 

This process involves two steps. In the first step, a,co-dihydroxy-terminated oligo(propylene succinate)s (SP) were prepared by the thermal polycondensation of excess diol and diacid, (see first part of Scheme 9). In the second step, the... 

Dihydroxy-y-butyrolaclones. 7-Butenolides (1) are oxidized by KMnOi in the presence of a erown ether (dicyclohexyl-18-crown-6) to mixtures of the c/s-diols 2 and 3 with some preferenee for the former. The stereoseleetivity is influeneed by the substituent at the y-position. It is highest with bulky y-alkoxymethyl groups and lowest with alkyl substituents. 

To rationalize the effect of structure and substituents on the acid- or base-catalyzed loss of water from a,/S-dihydroxy-substituted radicals, the complementary techniques of pulse-radiolysis and ESR spectroscopy have been employed in a kinetic study of the dehydration of a variety of a,/9-dihydroxyalkyl radicals [ CR (0H)CR R 0H] into the corresponding carbonyl-conjugated radicals [ CR R C(0)R ]. The overall rates of proton-catalyzed dehydration, as revealed by steady-state (ESR) and time-resolved (pulse-radiolysis) experiments, indicate the importance of the electronic effects of substituents (contrast values of 1.2 x 10 and 9.8 X 10 s for the radicals from cyclohexane-1,2-diol and butane-2,3-diol, respectively, with that for the radicals from erythritol of 4.2 x 10 m s ). Time-resolved experiments enable information to be obtained about the generation of the protonated species [ CR (0H)CR R 0H2 ] and the loss of water from this intermediate. 

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