Tert-butyldimethyl silyl

It should be noted that there are some limitations to the use of the tert-butyldimethylsilyl group (and, presumably, other trialkylsilyl groups) for the selective protection of hydroxyl groups. Isomerization between 0-2 and 0-3 occurs with 2 - and 3 -0-(tert-butyldimethyl-silyl) derivatives of nucleosides when they are in prolonged contact with silica gel,309 or when stored in aqueous pyridine, aqueous triethyl-... 

Imines are, preferably, used in the N-Boc-protected form less electrophilic N-allyl and N-benzyl imines gave unsuccessful results [36], The tert-butyldimethyl-silyl ketene acetals are the most suitable silyl ketene acetal substrates. It should be added that a low temperature is required to suppress an undesired uncatalyzed reaction that leads to racemates. 

Five steps were required to convert 75 into the iodide coupling partner 44 needed for union with dithiane 43 (Scheme 17.16). Thioacetal formation31 and concomitant deketalisation were instigated by reacting 75 with 1,3-propanedithiol under Lewis acid conditions. Triol 76 was isolated in 65% yield. The less-hindered primary hydroxyl of 76 was then selectively 0-tosylated, and the remaining hydroxyls masked as tert-butyldimethyl silyl (TBDMS) ethers. Iodide displacement on 77 with sodium iodide and copper bronze,32 and transketalisation with N-chlorosuccinimide (NCS)/silver nitrate33 finally secured 44. 

To a cooled solution of 3-methoxy-2-pyridyl 2,3.4-tri-0-benzyl-6-C>-tert-butyldimethyl-silyl-a-D-glucopyranosyl-(1 6)-2,3,4-tri-0-benzoyl-p-D-glucopyranoside 10 (134 mg, 0.117 mmol) (ot/p, 10 1) in 0.6 mL of THF were added 52 p,L of acetic acid and 0.46 mL of 1 A/ TBAP in THF. The resulting mixture was stirred at 0°C for 30 min, then at room temperature for 2 days, at which time TLC indicated the reaction was completed (BtOAc-hexane, 1 2). After the solvent was evaporated, EtOAc was added, the solution was washed with water and brine, and the organic layer was processed as usual. The residue was purified by flash chromatography on silica gel using EtOAc-hexane (1 1) as the eluant to afford 98 mg of a-linked product 12 and 10 mg of the p-anomer (a/p, 10 1 89%). 

RNA Synthesis. - Methods for the synthesis of RNA are now routine but less efficient than DNA synthesis. The most popular phosphoramidite reagents employ acyl protecting groups for the exocyclic amino functions of the nucleosides, dimethoxytrityl for the 5 -hydroxyl function and 2 -0-tert-butyldimethyl-silyl (tBDMS) for the 2 -hydroxyl function. The silyl protecting group is usually removed by treatment with IM TBAF or ti iethylamine.3HF. Acidic deprotection conditions have also been developed for removal of tBDMS groups. ... 

A similar behavior was observed in the synthesis of (5)-2-methylenecyclopropanemethanol (8). Cleavage of the j8-sulfonyl silyl group, together with removal of the tert-butyldimethyl-silyl protecting group from the alcohol, was accomplished in one step in 35% yield. With the alcohol protected as the benzyl ether and subsequently converted to a cyano group, however, elimination proceeded in 86% yield. 

The stereoselectivity of this cleavage reaction can be modulated by the size of the trialkylsilyl group and by the reactivity of the nucleophile, as demonstrated by the use of tert-butyldimethyl-silyl iodide and trifluoroacetate, respectively. ... 

Protection of hydroxy groups as the THP and tert-butyldimethyl silyl ethers and, conversely, deprotection of these derivatives to the original alcohols. 

Noami, M., M. Kataoka, and Y. Seto. 2002. Improved tert-butyldimethyl- silylation GC/MS detection of nerve gas hydrolysis prodncts from soils by pretreatment of aqueous alkaline extraction and strong anion-exchange solid- phase extraction. AwaZ. Chem. 74(18) 4709-15. 

Jadhav, V. H. Borate, H. B. Wakharkar, R. D. A simple method for deprotection of tert-butyldimethyl-silyl ethers by using stannous chloride under microwave irradiation. Indian J. Chem., Section B 2006, 45B, 322-324. 

The Determination of Terbutaline in Human Plasma by Selected Ion Monitoring of the tert-Butyldimethyl-silyl Ether... 

Obtained by deprotection of 3-[(tert-butyldimethyl-silyl)oxy]-3, 4,4, 5 -tetramethoxybenzophenone (SM) in... 

SM was prepared in two steps first, formation of N-[3-[(tert-butyldimethylsilyl) oxy]-4-methoxybenzoyl]morpholine (SMI) by action of 3-[(tert-butyldimethyl-silyl)oxy]-4-methoxy-benzoyl chloride with morphohne in toluene for 4 h at r.t. under argon. Then, the amide SMI was allowed to react with the hthium derivative prepared from 3,4,5-trimethoxybromobenzene [1178] and tert-butyllithium in tetrahydrofuran at -78° to give SM [1177]. 

Pilli and Victor reported on a concise synthesis of (—)-decarestrictine D 32, which uses an intramolecular Nozaki-Hiyama-Kishi reaction as the penultimate step. Aldehyde 33 was prepared via a Dess-Martin oxidation and immediately submitted to NHK conditions of CrCl2-0.5% NiCl2 (15 equiv) in DMF to afford the tert-butyldimethyl-silyl-protected (—)-decarestrictine D 34 (Scheme 12.31). 5-(Z)-7-Oxozeaenol, also known as LL-Z1640-2 35, was isolated in 1978 by McGahren et al. from an unidentified fungus Lederle culture 121640 and has attracted interest as a potent kinase inhibitor (Figure 12.4). ... 

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