Deacylation derivatives

A further group of AT-[(acyloxy)methyl] pro-moieties contains acidic and/or lipid-like substituents. Here again, most published results concern phenytoin. Thus, some phenytoin-lipid conjugates such as 8.183 and 8.186 (with R = various fatty acyl moieties) were reported [233]. Such prodrugs are, of course, insoluble in water but formed dispersions when briefly sonicated in EtOH/water mixtures containing sodium taurodeoxycholate. No significant hydrolysis was seen in buffer or plasma. In contrast, incubation with pancreatic lipase yielded the bis-deacyl derivatives (i.e., 8.182 and 8.185, respectively), with subsequent liberation of phenytoin the time for 50% liberation of phenytoin varied from 20 to 200 min under the conditions of the studies [233][234], The intermediates 8.182, 8.184, and 8.185 were also substrates for human and rat plasma hydrolases. 

The formation of deacylated derivatives 273 in acidic media may be explained by ipjo-protonation of acyl-chrysenes 270. On the other hand, they may also be explained by reactions at preceding stages by analogy with transformations known for monocyclic pyrylium salts (68TL4379 69JOC2736 72TL4439) (cf. Section III,C,4,d and III,F,2,c). Chrysenes... 

The H202-HF-SbF5 system has been applied by Jacquesy and co-workers in the hydroxylation of a variety of functionalized arenes.624 Hydroxylation of phenyl esters has been shown to afford themeta and para isomers as main products625 [Eq. (5.217)]. Substantial amounts of the deacylated derivatives were obtained in the reaction of phenyl formate and diphenyl carbonate. In the hydroxylation of 2-chlorophenyl and 4-chlorophenyl acetate, regioselectivity is controlled by the chlorine substituent with the hydroxyl entering into the meta position to the ester group.626 A similar effect was observed in the hydroxylation of anilines and anilides. 

The attachment and use of enzymes on hydrophilic supports covered with a dense layer of highly hydrophobic groups has been shown by Vita-Invest in recent years [78]. Various lipases were immobilized on Octyl-Sepharose CL-4B, and in certain cases an increase of activity of more than 100 times could be observed. The usefulness of these supported enzymes was demonstrated in first experiments by the regioselective hydrolysis of glucose pentaacetate (57) to glucose tetraacetate with Candida rugosa lipase (Scheme 18). The regioselectivity was found to be pH dependent, and the 2-0-deacylated derivative 58 could be obtained at pH 5, whereas the 6-0-deacylated product 59 was formed at pH 7. 

Unlike the MET-I acaricides and insecticides, the MET-III inhibitor acequinocyl is a pro-insecticide that requires biological activation for activity. Acequinocyl is hydrolyzed to the corresponding deacyl derivative, 2-hydroxy-3-n-dodecyl-l,4-naphthoquinone (DHN), in isolated mitochondria (Fig. 28.3.3) [76]. This is consistent with the observation of a time lag in MET inhibition with acequinocyl [76] and that acequinocyl itself does not directly inhibit MET activity [91]. 

Definition Deacylated derivative of chitin Properties M.w. 70,000 Toxicology TSCA listed Storage Hygroscopic... 

In the normal isomerization of humulone (70) the bond between C-1 and C-6 is broken and a new bond is formed between C-1 and the carbonyl group at C-5 (Fig. 14.6). The reversed isomerization of humulone (Fig. 14.8), in which the bond between C-5 and C-6 is broken and the new bond formed between C-5 and the carbonyl on C-1, has now been found to occur and the unti-products account for about 10% of the isomerization mixture [93]. By boiling humulone in a buffer solution at pH 11-0 the cis- and tmn.r-isomers of both acetylhumulinic acid (88) are formed. The bitter tasting hop acids known [94]. In the mixture of isomerization mixture are deacylated anti-derivatives deacyl-ated anti-isohumulone (90), deacylated anti-acetylhumulinic acid (91), and deacylated onti-humulinic acid (92) [93]. Deacylated humulone (89) is readily isomerized to these products whereas the deacylation of anti-isohumulone only occurs to a limited extent (< 2 %) so it has been proposed [95] that (90), (91) and (92) are formed via deacylated humulone (89). However, the relative ease of deacylation of humulone and [Pg.108]

LD50 (rat, ivn) 50 mg/kg. FM6125000 Partially deacylated deriv. See Chitosan in The Combined Chemical Dictionary. 

Obt. by acid or enzymic hydrol. of Partially deacylated deriv. Component of Chitin, C-58. Cryst. (MeOH aq.). 

The structures of antibiotics P-2563 (A) and (P) elaborated by Pseudomonas fluorescence P-2563 have been identified as (501 R = Ac) and (502). Antibiotics (501 R = Ac) and (502), as well as the N-deacylated derivative (501 R = H), were also found among the components of the antibiotic complex LL-AM31 produced by a Streptoverticillium species. The structure of the aglycone... 

The low yield of the hop bitter acid derivatives belonging to the anti-series is also related to the fact that the anti-rearrangement may occur after previous deacylation of humulone. Thus, a special series of compounds is formed, lacking the 3-methylbutanoyl side chain of humulone. All hop-alpha acids lead therefore, via this mechanism, to the same deacylated derivatives (Fig. 73). 

The total yield of the deacylated derivatives of the anti-series is 8.5%. When the anti-isohumulones and the anti-acetyihumulinic acids are included, the yield even exceeds 10%. This is certainly not negligible in comparison with the most important hop bitter acids, the isohumulones. 

The procedure is the same as that followed for the antl-isohumulones and the deacylated derivatives. The residue of the ether extract shows, after 1200 transfers in the two-phase system ether aqueous buffer pH 5.3, a band with K 0.58, containing compound 168 (0.045 g 0.3%). 

---