Dineopentyl acetal

Schotten-Baumann type N-benzoylation was carried out on trans-4-hydroxy-L-proline 34,39 giving amide 43 in a satisfactory yield of 65%. The disappointing yield here could be attributed to difficulties experienced in recrystallization of the product 43. The amide 43 was esterified to give tert-butyl ester 44 using a modification of a procedure described by Widmer40 with dimethylformamide-dineopentyl acetal and tert-butanol as reagents. This provided crystalline 44 in 71% yield from 43 with no evidence of terf-butyl ether formation at the C-4 hydroxyl group (Scheme 12). 

DECARBOXYLATIVE DEHYDRATION N,N-Dimethylformamide dineopentyl acetal. Triphenylphosphine-Diethyl azodicar-boxylate. 

OH pentofuranoses, as shown in Scheme 5. Thus, otherwise scarcely available D-allal and D-gulal derivatives can he readily prepared from D-ribose and D-arabinose, respectively [82]. It has recently been demonstrated that reductive elimination of /3-hydroxycarboxylic acid can be applied for preparation of hex-l-enitols. The procedure involves refluxing appropriate substrate in toluene with Al,lV-dimethylformamide dineopentyl acetal. 

Dimethylformamide dineopentyl acetal (3). Mol. wt. 231.37. Compare Dimethyl-formamide diethyl acetal. Supplier Fluka. 

Esterification Alumina. Boron trifluoride. Diazomethane. Dimethylformamide dimethyl acetal. Dimethylformamide dineopentyl acetal. Dimethyl sulfite. Diphenyidiazomethane. Ethyldicyclohexylamine. Ion-exchange resins. Isobutene. Methanesulfonic anhydride. 3 % Methanolic HCl (see Acetyl chloride). Methyl iodide. l-Methyl-3-p-tolyltriazine. Poly-phosphoric acid. Sulfosalicylic acid. Sulfuryl chloride. p-Toluenesulfonic acid. p-Tpluene-sulfonyl chloride. Triethylamine. Triethylorthoformate. Trifluoroacetic anhydride. Esterification of phosphoric acid Trichloroacetonitrile. 

Reaction of 2-hydrazinopurine 293 with diethoxymethylacetate or preferentially with N,N-Aimethy 1 lbrmamide dineopentyl acetal produced [l,2,4]-triazolo[3,4-/>]purine 294. This compound is a strong UV-fluorescence agent (82H(17)405) (Scheme 85). 

HCONH2, CH CONH. D imethy lacy lamines HC0N(CH,)2, CH,C0N(CH )2 (CH,)2NCH(0CH,)2 Dimethylformaldehyde dineopentyl acetate 1 -Benzy 1-1,4-dihydro-nicotinamide N,N -Diethylnicotin-amide... 

Dimethylformaldehyde dineopentyl acetal 1 -Benzyl-1,4-dihydro-nicotinamide N,N -Diethy Inicotin-amide... 

Dimethyl formaldehyde dineopentyl acetate 1-Benzyl-1, A-dihy dr o-nicotinamide N,N -Diethylnicotin amide... 

Subsequently, a more hindered DMF acetal such as DMF dineopentyl acetal 18 was used, and this time the desired product enaminone 19 was isolated in 80% yield. Treatment of the enaminone 19 with acid in refluxing acetic acid afforded the cyclized product 20 in 77% yield. 

Thymidine-5 -carboxylic acid and dimethylformamide dineopentyl acetal in dimethylformamide heated 4.5 hrs. at 80-90° l-(2, 3 -dideoxy-3, 4 -didehydro-) -D-erythrofuranosyl)thymine. Y 94%. - This reaction comprises a useful selective degradation of C-5 from a 2 -deoxynucleoside. F. e. s. J. 2emliSka et al.. Am. Soc. 94, 3213 (1972). 

Structural analogues of the formycins have been reported in a paper describing a general route to 2-glycosylated pyrimidinones (see Scheme 17). Treatment of formycin with iViV-dimethylformamide dineopentyl acetal gave the 2,5 -cyclo-nucleoside as one of the products, and 2, 3 -0-isopropylideneformycin was converted into the 4,5 -cyclonucleoside by way of the 5 -toluene-p-sulphonate. Adenosine deaminase caused deamination of the 2,S -cyclonucleoside only, indicating that the a //-conformation of a substrate is utilized by the enzyme. 

Dimethylformamide dineopentyl acetal Methyl from hydroxymethyl groups via 2-pyrimidinyl thioethers... 

A mixture of 2, 3 -0-isopropylideneuridine, 2-mercaptopyrimidine, and dimethyl-formamide dineopentyl acetal refluxed in benzene under anhydrous conditions -> thioether (Y 73%) refluxed 0.5 hr. with Raney-Ni W4 in ethanol 2, 3 -0-isopropylidene-5 -deoxyuridine (Y 70%). - This reaction affects prim, hydroxyl groups selectively therefore, protection of the functional groups is not required. F. e. s. A. Holy, Tetrah. Let. 1972, 585. 

Esterification with the dineopentyl acetal is very slow (benzoic acid, 80° in benzene, 1 hr —7% yield of ester) and this reagent is used conveniently as a catalyst in the direct esterification of acids and alcohols (benzyl and p-methoxy-benzyl alcohol) where for the alcohol k kneope tyi. Trans-acetalization occurs initially via the reaction (a). 

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