Benzyl group Subject

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... 

These compounds were to be subjected to conventional triflation by triflic anhydride, followed by treatment with potassium nitrite in DMF. It was expected that in all cases good inversion yields would be obtained with neighboring ester groups, whereas the inversion would be inefficient with benzyl groups. 

Recrystallization of thioamides 24f-h gave colorless or slightly yellow prismatic crystals [49]. All three thioamides were subjected to X-ray single crystal analysis, and it was revealed that they prefer the same conformation 24-1 in which a benzyl group was placed close to the thiocarbonyl group, the same as the major isomer in solution. The alkenyl double bonds are perpendicular to the thioamide group, and twist in the range of 87.9° to 100.5°. 

Benzyl groups are the second fiddles of the amine protection repertoire, and they are especially useful when a substrate is to be subjected to powerful orga-no metal lie reagents or metal hydrides which might attack a carbamate. Benzyl-amines are not generally cleaved by Lewis acids under preparatively useful conditions. The following discussion embraces benzylamines, diphenylmethylamines and their methoxy-substituted derivatives. 

Debenzylation. A benzyl group attached to the nitrogen atom of a carboxamide is subject to removal by NBS at room temperature/... 

Synthesis from d-glucose A stereospecific synthesis of nectrisine (1) has been achieved from diacetone D-glucose by conversion to 3 (Scheme 1). Catalytic reduction of 3 followed by acylation with trifluoroacetic anhydride afforded the trifluoroacetyl amides 4 (82%) and 5 (13%). Removal of the isopropylidene group from 4 afforded 6, which was subjected to oxidation with NaI04 followed by removal of the benzyl group and subsequent deacylation of the formyl and trifluoroacetyl groups to produce 1. 

In their approach the needed substrate 345 was prepared by using the aldol-hydroxamate methodology. After deprotection of the benzyl group in 345, followed by PCC oxidation of the resulting alcohol, the aldehyde 346 was subjected to treatment with sodium hydride to furnish the desired, but unstable, carbapenem 347. 

As before, the hydroxy group of this epoxy alcohol was subjected to a Mitsonobu esterification and subsequent cleavage of the resulting benzoate ester 14 to afford epoxy alcohol 15, with the desired relative stereochemistry, in 87 % yield over two steps. The free hydroxy group was protected, as previously, with a benzyl group in 96 % yield. 

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