Resorcinol homologues

A dipping solution consisting of 0.2% fast blue salt B in hydrochloric acid (c = 0.5 mol/1, immersion time 30 s) has been reported for the detection of resorcinol homologues [1]. 

Resorcinol see 1,3-Dihydroxybenzene Resorcinol homologues 290 Resorufin, pH-dependent change of fluorescence color 91... 

Structural information on aromatic donor molecule binding was obtained initially by using H NMR relaxation measurements to give distances from the heme iron atom to protons of the bound molecule. For example, indole-3-propionic acid, a structural homologue of the plant hormone indole-3-acetic acid, was found to bind approximately 9-10 A from the heme iron atom and at a particular angle to the heme plane (234). The disadvantage of this method is that the orientation with respect to the polypeptide chain cannot be defined. Other donor molecules examined include 4-methylphenol (p-cresol) (235), 3-hydroxyphenol (resorcinol), 2-methoxy-4-methylphenol and benzhydroxamic acid (236), methyl 2-pyridyl sulfide and methylp-tolyl sulfide (237), and L-tyrosine and D-tyrosine (238). Distance constraints of between 8.4 and 12.0 A have been reported (235-238). Aromatic donor proton to heme iron distances of 6 A reported earlier for aminotriazole and 3-hydroxyphenol (resorcinol) are too short because of an inappropriate estimate of the molecular correlation time (239), a parameter required for the calculations. Distance information for a series of aromatic phenols and amines bound to Mn(III)-substituted HRP C has been published (240). 

Higher plant resorcinolic lipids include very simple homologues of the orcino 1-type (l,3-dihydroxy-5-methylbenzene) phenols and a variety of homologues that are derivatives with the ring, chain or both ring and chain modified. Resorcinolic lipid molecules have a dual, aromatic and acyclic character. In most cases the side chain in resorcinolic lipids is odd numbered, which is relevant with regard to their possible biosynthetic pathway. 

The structures of over 120 identified natural resorcinolic lipid homologues are presented in Table 4 and Fig. (4) which lists the formulae of resorcinolic lipids and relevant references to previous and current studies. 

These results and those now discussed which show the ability of resorcinolic lipids to incorporate and modulate phospholipid bilayer properties, suggest a possible similar role in biological membrane-related enzymatic activities. It has been demonstrated that at a concentration of 10 5 M, long-chain resorcinolic lipids, caused a decrease of apparent acetylocholinesterase activity in the erythrocyte membrane while simultaneously stimulating the activity of Ca2+-dependent ATPase [348]. The inhibition of erythrocyte acetylcholinesterase has been also observed for other phenolic lipids (Stasiuk and Kozubek - unpublished work) and a similar effect of one of the homologues, namely tridecylresorcinol shown towards Na+-K+ ATPase [157]. a-Glucosidase and aldolase were also inhibited by resorcinolic lipids isolated from cashew [283]. 

Studies of the kinetics of pancreatic phospholipase A2 hydrolysis in a phosphatidylcholine bilayer modified by alkyl(en)ylresorcinol homologues also suggests the same possibility. It was shown that 5-n-heptadecyl and 5-n-heptadecenyl resorcinols when incorporated into liposomal membranes at a concentration of 4 mol%, and lower, caused a drastic increase of the latency phase of the enzyme, the period of time during which redistribution of the products within the bilayer occurs... 

It should be stressed that due to very high values of buffer-membrane partition coefficients and low CMC values, the effect of resorcinolic lipids injected into the external medium is different from the effect observed when they were present internally in the membrane. For instance, the same homologues that are highly hemolytic when injected into erythrocyte suspension are not lytic when injected in the form of phosphatidylcholine-resorcinolic lipid liposomes, which indicates that direct exchange of resorcinolic lipids between membranes is limited. 

While the majority of the syntheses discussed have been directed to the orsellinic acids and their homologues, keto and cyano analogues have also been prepared in the monocyclic series. The ketoester shown afforded the salicylate upon cyclisation with sodium ethoxide or magnesium methoxide and none of the resorcinol although an excess of magnesium ethoxide gave a mixture of both products (refe. 32, 33, and 34). 

Fries rearrangement of resorcinol diacetate (404) with ferric chloride provided 4,6-diacetyl-resorcinol (406). The benzodipyrazole (40) has been best prepared from (406) by treatment with hydrazine hydrate in 2-methoxyethanol (Scheme 19). The 8-methyl homologue (41) of (40) has been prepared in similar fashion <88JMC2034>. 

Xylenols (aU six isomers) are now also in common use to form alkali-resistant grades of phenolic resins. High 3,5-xylenol mixtures are preferred. Also, resorcinol, which forms very reactive phenolic resins, is used in preparations of cold-setting adhesives. Higher homologues of phenol, like Bisphenol A, are used to prepare special phenol-formaldehyde condensates. 

In analogy to their resorcinol-formaldehyde homologues, polyurethane wet gels are synthesized by polycondensation. Subsequently, aerogels are commonly obtained by supercritical fluid drying of the organic wet gels [23]. 

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