O-Bis trimethylsilyl acetamide

Gas chromatographic separation of amphenicols is further complicated by the need for derivatization of their polar functional groups. Silyl derivatives formed by treating sample extracts with N,O-bis(trimethylsilyl)acetamide (49), trimethylsilyl N,N-dimethyl carbamate (47), N,O-bis(trimethylsilyl)tri-fluoroacetamide/trimethylchlorosilane (99 1) mixture (32, 51), or mixture of... 

HFAA, heptafluorobutyric acid anyhydride BSTFA, N,O-bis(trimethylsilyl)tnfluoroacetamide 3 -hydroxysteroid dehydrogenase BSA, N,O-bis(trimethylsilyl)acetamide MSTFA, N-methyl-N-(trimethylsily)trifluoroacetamide TMS, trimethylsilane SEA, supercritical-fluid extraction PFBCMO, pentafluorobenzylcarboxymethoxime. 

Gas chromatography is used to analyze volatile derivatives of amino acids. Phenylthiohydantoins (products of Edman degradation) may be analyzed directly by GC but are better resolved if converted to their trimethylsilyl derivatives with N, O-bis(trimethylsilyl) acetamide. Free amino acids are generally converted to their 7V-trifluoroacetyl- -butyl esters or trimethylsilyl derivatives before GC analysis. For best results, all gas chromatography of amino acid derivatives should be done with a glass column and injection port, as contact with metals causes extensive decomposition of the derivatives. 

Scheme 2.27 Enantioselective molybdenum-catalysed allylic alkylation of linear arylpropenyl carbonates (BSA = N, O-bis(trimethylsilyl)acetamide).

Chlorophenyl)glutarate monoethyl ester 87 was reduced to hydroxy acid and subsequently cyclized to afford lactone 88. This was further submitted to reduction with diisobutylaluminium hydride to provide lactol followed by Homer-Emmons reaction, which resulted in the formation of hydroxy ester product 89 in good yield. The alcohol was protected as silyl ether and the double bond in 89 was reduced with magnesium powder in methanol to provide methyl ester 90. The hydrolysis to the acid and condensation of the acid chloride with Evans s chiral auxiliary provided product 91, which was further converted to titanium enolate on reaction with TiCI. This was submitted to enolate-imine condensation in the presence of amine to afford 92. The silylation of the 92 with N, O-bis(trimethylsilyl) acetamide followed by treatment with tetrabutylammonium fluoride resulted in cyclization to form the azetidin-2-one ring and subsequently hydrolysis provided 93. This product was converted to bromide analog, which on treatment with LDA underwent intramolecular cyclization to afford the cholesterol absorption inhibitor spiro-(3-lactam (+)-SCH 54016 94. 

After library synthesis and solid-phase assay of 100,000 beads on a red-labeled synthetic receptor [23], 55 deep staining beads were selected and their code was released via photolysis at 350 nM the released alcohols were silylated with N, O-bis(trimethylsilyl) acetamide and injected into a capillary GC with EC detection decoding 52 different structures, which are shown in Figure 9.7. 

Experimental conditions molar ratio substrate/catalyst/dimethyl malonate/ N.O-bis(trimethylsilyl)acetamide/potassium acetate = 100/1/200/200/10. Catalyst 0.006 mmol, solvent 4 mL, room temperature. 

To prepare the corresponding cytosine containing nucleoamino acid 9, N -Boc cytosine was first silylated using N,0-bis(trimethylsilyl)acetamide (BSA) under carefully controlled conditions to produce mono-silylated-N -Boc cytosine 7. The mono-silylated product 7 undergoes l2-mediated nucleosidation with the O-MTM... 

Alternative silylating reagents such as N,0-bis(trimethylsilyl)acetamide 22a (BSA) [39-43], N,0-bis(trimethylsilyl)trifluoracetamide 22b (BSTFA) [44], or N,N-bis(trimethylsilyl)formamide 22c (BSF) [41, 46], in which the N- and O-trimethyl-silyl groups are in equilibrium [45] (Scheme 2.4), are much more powerful silylating reagents [40, 45] but are more expensive than FIMDS 2, because they are usually prepared by heating formamides or acetamides with TCS 14/triethylamine... 

A wide variety of acidic compounds has been trimethylsilylated, and the preferred procedure is to treat the sodium, calcium, or barium salt, as a suspension in pyridine, with bis(trimethylsilyl)acetamide and chlorotrimethylsilane 100,163,164 this gives the trimethylsilyl ester of the O-trimethylsilyl derivative. Lead salts may be used,165 or the potassium salt may be used in methyl sulfoxide, the O-trimethylsilyl derivative becoming concentrated in the upper phase.166... 

M. Matsuo, R. Takano, K. Kamei-Hayashi, and S. Hara, A novel regioselective desulfation of polysaccharide sulfates Specific 6-O-desulfation with N, 0-bis(trimethylsilyl)acetamide, Carbohydr. Res.,2A (1993) 209-215. 

Macrocyclization by allylation-alkylotion. The key step in a synthesis of the antibiotic A26771B (3) is cyclizationof the substrate 1 using O.N-bis(trimethylsilyl)acetamide (1, 61 2, 30 3, 23-24) as base and Pd[P(ChH,),]4 as catalyst. In addition a bidcntate phosphorus ligand is essential. The highest yields were obtained with 1,4-bis(diphenylphosphine)butane (dppb). 

A newer method for the preparation of nitronic esters, namely utilizing the O-trimethyl-silyl ester, has been reported and these are prepared by the reaction of alkylnitro compounds and Af,iV-bis(trimethylsilyl)acetamide. These nitronic esters also undergo cycloaddition with alkenes to produce isoxazolidines (equation 54) (74M1P41601,74DOK109, 78ACS(B)118). 

Nucleotide phosphates. Nucleotide H-phosphonates are oxidized to the phosphates in dichloromethane by bis(trimethylsilyl) peroxide in the presence of N.O-bis(triraethylsilyl)acetamide and a catalytic amount of Me,SiOTf. 

DaptaeemeM 0/ o/fyfiV ge d/aerrores. in the presence of Pd(dppeV 2 catalyst and O.N,bi (trimethylsilyl)acetamide as base, one aoetoxy group of an allyltc gem-diacctate can be disf aced by a stabilized nucleophile. 

Fig. 3. (Top left) Chemical methods used to depolymerize the polyesters. (Top right) Thin-layer and gas-liquid chromatograms (as trimethylsilyl derivatives) of the monomer mixture obtained from the cutin of peach fruits by LiAlD4 treatment. In the thin-layer chromatogram the five major spots are, from the bottom, C18 tetraol, C16 triol, and C18 triol (unresolved), diols, and primary alcohol. Nx = C16 alcohol N2= C18 alcohol Mj = C16 diol M2 = C18 diol D = C16 triol D2 and D3 = unsaturated and saturated C18 triol, respectively, T4 and T2, unsaturated and saturated C18 tetraol, respectively. (Bottom) Mass spectrum of component D3 in the gas chromatogram. BSA = bis-N,O-trimethylsilyl acetamide...

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