P-bromobenzoate esters

The natural occurrence of cycloartane triterpenoids has been reviewed.25 Acid hydrolysis of lyofolic acid, a glucoside from the leaves of Lyonia ovalifolia, afforded lyofoligenic acid (19) whose structure was established by X-ray analysis of the 3a-O-p-bromobenzoate methyl ester.26 The constitution of the genuine aglycone, protolyofoligenic acid (20), was confirmed by interrelation with cycloartenol.27... 

In the following, selected examples for these reactions are reported. Reaction a) has been discussed in some detail already in Section IV. C examples for reaction d) are found in Section VI. A. Selective transbutylation (reaction b)) was achieved for various mono-, di- and triethers or esters of calix[4]arene, leading to tri-, di- and mono-t-butyl calix[4]arene derivatives, from which the 0-aUtyl and especially the O-acyl residues can be cleaved again if desired, or necessary. A single f-butyl group was also eliminated from the tetramethyl ether of 2b , the pentamethyl ether of and the hepta(p-bromobenzoate) of 2e °. Various other partially debutylated derivatives of 2c have been prepared analogously . ... 

Criticai data (a) FABMS m/z 1411 [M+H]+, m/z 1388 [M-H]-, (b) swinhoiide A tri-p-bromobenzoate derivative gave the compiex Fl NMR spectrum, (c) the monomeric methyi ester was obtained by treatment with NaOMe. 

An X-ra.y crystallographic study of the p-bromobenzoate of cephalotaxine has verified the constitution and relative stereochemistry of this alkaloid and its esters (13a—c) and has established for the first time the 4S absolute configuration as depicted by (20 R = COCeH4-p-Br). ... 

A discontinuity in the thermodynamic properties and phase behaviour of the cholesteryl n-alkanoates between Cg and Cg is matched by a distinct difference between the crystal structures of the octanoate and nonanoate. The nonanoate chains pack with cholesteryl ring systems rather than with each other, the molecules lying antiparallel. The decanoate, undecanoate, and laurate (dodecanoate) show very similar crystal structures to the nonanoate. X-Ray data are also reported for a series of polymerizable liquid-crystalline cholesteryl esters,and for petrosterol p-bromobenzoate, which is shown to have the structure (5), and not the side-chain (6) as reported in 1978. 

The bromine atoms of m- and p-bromobenzoic acids and o-bromobenzoates can be displaced by acrylate, crotonate, and methacrylate esters in the presence of palladium. The reaction seems applicable to the synthesis of a wide variety of... 

Bromobenzoic acid (p-bromobenzoic acid) [586-76-5] M 201.0, m 251-252 , 254-256 , 257-258 , pK 3.96. Ciystallise the acid from MeOH, or MeOH/water mixture, 90% EtOH and Et20. The methyl ester has m 81 from Et20 or dilute MeOH. The anilide has m 197° (from EtOH). [Male ThovpJ Am Chem Soc 35 269 1913, Lamneck Chem Soc 76 406 1954, Vandenbelt et al. Anal Chem 26 926 1954, Beilstein 9 IV 1017.]... 

X-Ray diffraction studies on corynoline p-bromobenzoate and (+)-14-epicorynoline bromoacetate have confirmed that the B/C fusion is cis in the former ester, and trans in the latter. 

C Fusidic acid methyl ester p - bromobenzoate (absolute configuration)... 

The ready availability of arylboronates by an aromatic C-H borylation provides a synthetic link to the well-established palladium-catalyzed cross-coupling reactions, rhodium-catalyzed 1,4-addition to a,p-unsaturated carbonyl compounds, and other bond forming reactions using arylboronic esters (Scheme 2.12). Borylation of 1,3-dichlorobenzene with pinacolborane is followed directly by a cross-coupling reaction with methyl p-bromobenzoate for the synthesis of a biaryl product in 91% yield [60]. Pinacol esters of arylboronic acids react much slower than the free acids [62], but both derivatives achieve high isolated yields and comparable enantioselectivities (91% ee) in asymmetric 1,4-addition to N-benzyl crotonamides [63]. Borylation of arenes followed by oxidation of the C-B bond is synthetically equivalent to an aromatic C-H oxidation to phenols [64]. Oxidation of the resulting arylboronates with Oxone in a 1 1 acetone-water solution is completed within 10 min at room temperature. 

C2 6H3 iBrOs, 3a, 11 a, 17/3-Trihydroxy-1 3a-C-nor-5/3-androstane-11 /3-carb-oxylic acid 1 la,17-lactone 3-p-bromobenzoyl ester, 33B, 196 C2 6H3 2Br04, 1 7/3-Hydroxy-1 0/3-methoxy-est r-4 (5) -en-3-one p-bromobenzo-ate, 41B, 607... 

C39Hs3Br07, Fusidic acid methyl ester 0-p-bromobenzoate, 33B, 204... 

Strains of Pseudomonas putida are very versatile in metabolizing aromatic compounds, particularly to the corresponding 1,2-dihydro-l,2-diols. The hydroxylating enzyme of the P. putida mutant is not strongly substrate specific and alkyl, aryl and halogen functionalities are usually readily tolerated380. Thus, 4-bromobenzoic acid (1, R = Br) is converted to a. v-4-bro-mo-5,6-dihydroxy-l, 3-cyclohexadiene-l-carboxylic acid (2, R = Br) in 80% yield with 98% cc (determined by chiral NMR shift experiments on the 4-nitrobenzyl ester) 375. The absolute stereochemistry, (5R,6R), was determined by a single crystal X-ray analysis. 

Arylation of p-dicarbonyl compounds (5,163-164). Experimental details are available for the preparation of homophthalic acids by arylation of jj-keto esters with 2-bromobenzoic acids with copper catalysts. ... 

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