Monobenzylation

Suggest a chemical test that would permit you to distinguish between the two glycerol monobenzyl ethers shown... 

Zn(BH4)2, TMSCl, Et20, 25°, 45 min, 77-97% yield. In this case reduction takes place to form a monobenzyl derivative of a diol. 

BnX (X = Cl, Br), Ag20, DMF, 25°, good yields. This method is very effective for the monobenzylation of diols. ... 

A cinnamoylpiperazine is described as an anti anginal agent. The key intermediate 1 can, in principle, be obtained by alkylation of the monobenzyl derivative of piperazine 71 with ethyl bromoacetate (72). Removal of the protecting group then affords the substituted piperazine (73). Acylation of this with 3,4,5-trimethoxycinamoyl chloride gives cinepazet (74). ... 

Alkylation of the monobenzyl ether of hydroquinone 34 with mesylate 35, gives ether 36. Hydrogenolytic removal of the benzyl group gives phenol 37. This affords cicloprolol (38) when subjected to the standard alkylation scheme 17]. In much the same vein, alkylation of g-hydroxy-phenylethanol 39, obtainable from the corresponding phenylacetic acid, with epichlorohydrin... 

The required monobenzyl phenylmalonate, MP 68°C, was prepared by treating a mixture of phenylmalonlc acid (18 g) and benzyl alcohol (13 g) in carbon tetrachloride (80 ml) with dry hydrogen chloride. 

Monobenzyl phenylmalonate (13.3 g) in dry benzene (100 ml) was refluxed with thionyl chloride (6.45 g) for 90 minutes, then concentrated in vacuo. The residual oil was dissolved In dry acetone (50 ml) and added to a stirred, ice-cooled solution of 6-aminopenlcillanic acid (9.7 g) in N sodium bicarbonate solution (135 ml), water (150 ml), and acetone (300 ml). The mixture was stirred for 30 minutes at 0°C and then for 90 minutes at room temperature, then concentrated under reduced pressure to remove acetone. The aqueous solution was brought to pH 2 with dilute hydrochloric acid and extracted with ether (3 X 100 ml). The ether solution was washed with water and then itself extracted with sufficient N sodium bicarbonate solution to give an aqueous phase of pH 7,5. The aqueous layer was separated and evaporated at low temperature and pressure to leave the Impure sodium salt of a-(benzyloxycarbonyl) benzylpenicillin. 

A mixture of monobenzyl-3-thienylmalonate (1.38 g, 5 mmol) and thionyl chloride (2.5 ml) was warmed at 50°C to 55°C for 1 hour, then at 60°C to 65°C for 10 minutes. The excess of thionyl chloride was removed in vacuo at not more than 30°C, the last traces being removed by codistillation with dry benzene (1 ml) under high vacuum, leaving monobenzyl-3-thienylmalonyl chloride as a yellow oil. 

The homology between 22 and 21 is obviously very close. After lithium aluminum hydride reduction of the ethoxycarbonyl function in 22, oxidation of the resultant primary alcohol with PCC furnishes aldehyde 34. Subjection of 34 to sequential carbonyl addition, oxidation, and deprotection reactions then provides ketone 21 (31% overall yield from (—)-33). By virtue of its symmetry, the dextrorotatory monobenzyl ether, (/ )-(+)-33, can also be converted to compound 21, with the same absolute configuration as that derived from (S)-(-)-33, by using a synthetic route that differs only slightly from the one already described. 

C7H 04S 21080-92-2) see Ticarcillin 3-thienylmalonic acid monobenzyl ester monochloride (C14H11CIO3S 50893-38-4) see Temocillin 3-thienylmalonic acid monophenyl ester monochloride (CnH.jC10,S 59/18-37-5) see Temocillin... 

The ene reaction of fuUerene (C o) with 3-methylene-2,3-dihydrofuran gives an easily isolated addition product in good yield <96JOC2559>. There is a continuous need for chiral acrylate esters for asymmetric Diels-Alder reactions with high diastereoselectivity. Lewis acid promoted Diels-Alder reactions of acrylate esters from monobenzylated isosorbide 28 (or isomannide) and cyclopentadiene provided exclusively e db-adducts with good yields and high diastereoselectivity <96TL7023>. 

Tanner [3,10] used essentially the same methodology for the conversion of a monobenzyl derivative of a C2-symmetric epoxy bis-alcohol into the corresponding derivative 6 of a C2-symmetric aziridine bis-alcohol (Scheme 3). 

The pronounced proclivity of phosphoric monoester monoanions to eliminate POf is not always recognizable from the characteristic pH profile of Fig. 1. The hydrolysis rate maximum at pH w 4 may be masked by a faster reaction of the neutral phosphoric ester, as in the case of a-D-glucose 1-phosphate63) or on hydrolysis of monobenzyl phosphate 64). In the latter case, the known ability of benzyl esters to undergo SN1 and SN2 reactions permits fast hydrolysis of the neutral ester with C/O bond breakage. The fact that the monoanion 107 of the monobenzyl ester is hydrolyzed some 40 times faster than the monoanion 108 of the dibenzyl ester at the same pH again evidences the special hydrolysis pathway of 107, rationalized by means of the metaphosphate hypothesis. 

Catalytic hydrogenolysis of the monobenzylated compound (23), however, provided the desired Boc-neonactin A (24) in 76% yield (Scheme 4.98). 

The reaction of monobenzylated isosorbide D with ditosylates (Eq. 35) is more subtle the microwave-specific effect (Tab. 3.15) appeared when the temperature was lowered to 80 °C (modulated by the presence of cyclohexane) whereas it was masked by a higher temperature of 110 °C (maintained by the use of toluene) [89]. 

Tab. 3.15 Yield (% E) from reaction of monobenzylated isosorbide (D) with ditosylates for 15 min.

The selectivity in favor of the desired monobenzylated product was found to be >99% and the immobilized Pt02 was found to be 4-5 times more active than the commercial Adams catalysts. In solution or in immobilized form, the PtOz colloid is effective in the hydrogenation of carbonyl compounds or of olefins. Recently, the heterogeneous catalytic amination of aryl bromides by immobilized Pd(0) particles has been reported [163], Secondary amines such as piperidine and diethyl amine are used in the amination of aryl bromides and the reaction proceeds with good turnover numbers and regio-control. The catalysts can be reused repeatedly without loss of activity or selectivity after filtration from the reaction mixture. 

Fujino, A., Asano, M., Yamaguchi, H., Shirasaka, N., Sakoda, A., Ikunaka, M., Obata, R., Nishiyama, S. and Sugai, T., Bacillus subtilis epoxide hydrolase-catalyzed preparation of enan-tiopure 2-methylpropane-l,2,3-triol monobenzyl ether and its application to expeditious synthesis of (R)-hicalutamide. Tetrahedron Lett., 2007, 48, 979. 

Studies on health effects of PAEs in humans have remained controversial due to limitations of the study design. Some findings in human populations are consistent with animal data, suggesting that PAEs and their metabolites produce toxic effects in the reproductive system. Some studies associate monoesters PAEs with semen parameters, sperm DNA damage, and hormones in human population, but none of them are statistically significant. Urinary monomethyl phthalate (MMP), monobenzyl phthalate (MBzP), mono- -butyl phthalate (MBP), MEHP, and monoethyl phthalate (MEP) were associated with poor sperm morphology and vigor, and with low sperm concentration, motility, and linearity [31-35]. However, it is not yet possible to conclude whether phthalate exposure is harmful for human reproduction. 

The first task was to design a linker between the primary amine functionality on the resin and the hydrazine function that ultimately binds the macrocyclic aldehyde. As mentioned above, the employed resin (PEGA1900) features a primary amino group at the end of a PEG spacer connected to the polyacrylamide backbone. To assure monofunctionalization, the amino group was monobenzylated, thereby preventing possible proximity problems. Subsequently, the resulting secondary amine was provided with a handle for the introduction of the hydrazine functionality (see Scheme 29). 

Compound 10 was converted into allyl glycoside 11 in 73 yield in two steps, (a) Bu2Sn0CH2CH=CH2—SnCl,(4), and (b) MeONa—MeOH. Treatment of 11 with dimethoxypropane and TsOH, and then with benzyl bromide— NaH—DMF afforded compound 12 in 51% yield. Solvolysis of compound 12 in MeOH—AcOH, and then monobenzylation by the stannylation— alkylation method(5) gave the desired glycosyl acceptor 8 in 67% yield. Acetylation of compound 8 and then deallylation with PdCl2— AcONa in aq.AcOH(6) afforded a 93% yield of hemiacetal 13, which was treated with (a) SOCI2—DMF in dichloroethane(7) and (b) AgF— CH CN(8) to give the desired fluoride 9 in 73% overall yield. 

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