Hydroxyl substitution

In Problem 4 25 you were asked to draw the preferred conformation of menthol on the basis of the information that menthol is the most stable stereoisomer of 2 isopropyl 5 methylcyclo hexanol We can now completely descnbe (—) menthol structurally by noting that it has the R con figuration at the hydroxyl substituted carbon... 

An old name for benzene was phene and its hydroxyl derivative came to be called phe nol This like many other entrenched common names is an acceptable lUPAC name Likewise o m and p cresol are acceptable names for the various ring substituted hydroxyl derivatives of toluene More highly substituted compounds are named as deriv atives of phenol Numbering of the ring begins at the hydroxyl substituted carbon and proceeds m the direction that gives the lower number to the next substituted carbon Sub stituents are cited m alphabetical order... 

These relationships are general Hydroxyl substituted purines and pyrimidines exist in their keto forms ammo substituted ones retain structures with an ammo group on the ring The pyrimidine and punne bases m DNA and RNA listed m Table 28 1 follow this general rule Beginning m Section 28 7 we 11 see how critical it is that we know the cor rect tautomeric forms of the nucleic acid bases... 

As tannins contain many phenolic -type subunits (Fig. 3), one may be tempted to think that they will exhibit a similar reactive potential to that of phenol, and that therefore procedures used in standard PF production can be transferred to those containing tannin. This, however, is not the case. The real situation is that tannin is far more reactive than unsubstituted phenol due to the resorcinol and catchecol rings present in the tannin. This increase in hydroxyl substitution on the two aromatic rings affords an increase in reactivity to formaldehyde by 10 to 50... 

Such aldolase-catalyzed bidirectional chain elongation ( tandem aldolization) of simple, readily available dialdehydes has been developed into an efficient method for the generation of higher carbon sugars (e.g. (87)/(89)) by simple one-pot operations (Figure 10.32) [126,156]. The choice offuranoid (87) or pyranoid (89) nature of the products can be determined by a suitable hydroxyl substitution pattern in a corresponding cycloolefinic precursor (86) versus (88)). The overall specific substitution... 

Every time a hydroxyl substitutent is replaced by an alkoxyl, a correction of 0.66 is added °° this is based on the increments observed for H3PO4 and its mono and dialkyl esters. 

Huen MSY, Kwok-Min H, Leung JWC, Sigel E, Baur R, Wong JTF. Naturally occurring 2 -hydroxyl-substituted flavonoids as high-affinity benzodiazepine site ligands. Biochem Pharmacol 2003 66 2397-2407. 

Internal cyclopropane ring-opening reactions have also been developed using hydroxyl-substituted cyclopropanes. A typical example of this strategy comes from the reaction of the polycylic alcohol 131, which reacts quantitatively with Hg(OAc)2 to yield the acetal 132 (Equation (45)).165 Carbonate moieties can also be used as internal nucleophiles as, for example, in the case of 133, which affords 134 in a 60% yield upon reaction with Hg(OCOCF3) (Equation (46)).166... 

Other conversions of hydroxyl-substituted compounds (or their lactam tautomers), their thio analogues, as well as amines are listed in Table 8. These reactions involve 0-, N-, or -alkylations or acylations, O-S exchange reactions, or other analoguous processes. 

Table 8 Various chemical transformations of hydroxyl-substituted compounds (or their lactam forms), their thioxo analogues, and amines...

Diastereoselective Cr(CO) complexes.2 Anisoles substituted in the orthoposition by a hydroxyl-substituted side chain can undergo diastereoselective... 

The novolac sample, which was provided by Kodak, was synthesized from pure meta-cresol and formaldehyde. It has a weight average molecular weight of 13,000 and a very broad polydispersity of 8.5. The polymer was purified by two precipitations from tetrahydrofuran into hexane. The PAC was a naphthoquinone-1,2-(diazide-2-)-5-sulfonyl ester provided by Fairmount Chemical (Positive Sensitizer 1010). A hydroxyl substituted benzophenone is attached to the sulfonyl ester. The spreading solvent was isopropyl acetate, which was obtained from Aldrich Chemicals and used as received. 

Following on directly from the suggestion of Childs et al. (1986a) that the 1-ethoxy-substituted homotropylium ion is not homoaromatic, Scott et al. (1986) presented NMR evidence for the diminution in homoaromaticity through a series of hydroxy-substituted homotropylium cations. They correlate the observed decrease in chemical shift difference between the H(8) (exo) and H(8) (endo) protons (AS) with a diminishing ring current and hence reduced homoaromaticity. The parent homotropylium cation [12] is considered to be the most homoaromatic and the order of homoaromaticity for monohydroxy substitution, based on A8 values, is [12] 4-OH > 2-OH > 1-OH > 3-OH (where 1-OH, 2-OH, etc., refers to the position of hydroxyl substitution on [12]). 

C. F. Correia, R. M. Borges dos Santos, S. G. Estacio, J. P. Telo, B. J. Costa Cabral, J. A. Martinho Simoes. Reaction of para-Hydroxyl-substituted Diphenylmethanes with tert-Butoxy Radical. Chem. Phys. Chem. 2004, 5, 1217-1221. 

HYDROXYL-SUBSTITUTED WATER-SOLUBLE TERTIARY PHOSPHINES... 

While fiavonoids have the 2-phenylchromen-4-one backbone, isoflavonoids (Fig. 8) have the 3-phenylchromen-4-one backbone, with no hydroxyl substitution at position 2 in the case of isofiavones. In contrast with the parent class of fiavonoids, the distribution of the isoflavonoid class in the plant kingdom is relatively limited, probably owing to the sporadic occurrence of isoflavone synthase. Isoflavonoids... 

Functional groups. Halogen substitution to an aromatic compound renders it less degradable. The number of substitutions and the location are important. Chlorophenols are an excellent example of increasing resistance with increasing substimtion. Amino and hydroxyl substitutions often increase degradability. 

Another parameter investigated was the usefulness of different substituents other than hydrogen or hydroxyl on the Of-carbon. Table II provides the relative activity of several diphenylmethyl substituted 5-pyrimidines. Clearly, the hydroxyl substituted compound is the most active against bean powdery mildew. 

Direct acylation of imines 238 produces stable hydroxyl substituted pyrrolo-benzodiazepines 239 (Equation (29) (1993TL1929)). 

L. A. Paquette and S. Z. Dong, Stereoselective synthesis of beta-anomeric 4 -thiaspirocyclic ribonucleosides carrying the full complement of RNA-level hydroxyl substitution,./. Org. Chem., 70 (2005) 5655-5664. 

Figure 4. Relative oxidation rates of various aromatic alcohols. Para-hydroxyl substitution eliminates substrate oxidation.

Stanjek, H. (1991) Aluminium-und Hydroxyl-substitution in synthetischen und natur-lichen Hamatiten. Dissertation, Techn. Univ. Miinchen, 194 p. 

Hydroxyl-substituted naphthimidazoles, benzothiazoles, benzimidazoles, benzotriazoles, benzoselenazoles and benzoxathiolones may be regarded as substituted phenolic couplers. Compound (121) is a specific example of the latter type which yields intense brown images (51USP2547843). In the absence of hydroxyl groups, alkyl-substituted derivatives of imidazoles or thiazoles may be couplers in their own right by virtue of their active alkyl substituent. 

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