Reversible hydrophobization and lipophobization of cellulose fibers via trifluoroacetylation

The surface modification of cellulose fibers with trifluoroacetic anhydride (TFAA) was studied using the heterogeneous cellulose/TFAA/pyridine/toluene system. The degree of substitution (DS) of the ensuing trifluoroacetylated fibers ranged from 0.04 to 0.30. This treatment conferred a high degree of both hydrophobicity and lipophobicity on the fibers' surface, even at low DS values. Both the dispersive and the polar contributions to the surface energy were drastically reduced. However, the original cellulose hydrophilicity could be readily restored through hydrolysis, by treating the modified fibers with neutral water.     

Formation of 17beta-alkoxy-16-keto steroids by reaction of 16alpha-hydroxy-17-keto and 17beta-hydroxy-16-keto steroids with trimethylsilyl iodide in the presence of alkyl alcohols

16Alpha-hydroxy-17-keto steroids, 1, 3, and 8, and their 17beta-hydroxy-16-keto isomers, 4, 5, and 9, were transformed into the corresponding 17beta-alkoxy-16-keto derivatives on treatment with trimethylsilyl iodide (TMSI) in the presence of alkyl alcohol in CHCl3 in poor to high yields.     

A facile strategy to prevent trifluoroacetylation of N-terminal proline peptides

Unwanted trifluoroacetylation occurred at the N-terminus of prolinyl peptides during detachment from the solid phase. This was observed when the N-α-Fmoc protecting group had been removed prior to the final TFA treatment. Subtly changing the SPPS protocol and incorporating Boc- in place of the Fmoc-protected proline as the N-terminal building block efficiently suppressed this side reaction.     

Direct microwave promoted trifluoroacetylation of aromatic amines with trifluoroacetic acid

A simple microwave-promoted procedure has been developed for the direct preparation of trifluoroacetanilides. An equimolar mixture of substituted anilines and trifluoroacetic acid was microwave irradiated at short reaction times, giving the corresponding anilides in high yields and purity.     

Acetylation of lagochilin

The acetylation of lagochilin and its derivatives with acetic anhydride in the presence of pyridine has been studied by PMR spectroscopy. It has been shown that the manifestation of the polyfunctionality of lagochilin in acetylation reactions with acetic anhydride is connected with a change in the nature of the process of solvation of the reaction forms with the subsequent replacement of the hydrogen atoms of the hydroxy groups by acetyl groups.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 46–49, January–February, 1980.     

Transformed steroids—part 95 : High pressure induced 1,3-dipolar cycloaddition of nitronic esters to 16-dehydro-20-oxo steroids

High pressure induced cycloaddition of Z and E nitronic esters (2) to 16-dehydro-20-oxo steroids (1) leads to regiospecific formation of steroido [16α,17α-d] tetrahydro-l',2'-oxazoles (3 and 4). It is shown that both modes (“exo-endo”) of dipolarophile approach to the dipole are realized for most steroids examined. All four possible isomers are isolated and their preferred conformations are established. It is shown that conversion of unstable stereomers to stable ones (3'→ 4; 4'→ 3) proceeds as a simultaneous nitrogen inversion and isoxazolidine cycle conformational change (_NE→E^N).     

Transformed steroids Communication 152. Photocycloaddition of 1-pentyne to 16-dehydropregnenolone acetate

Conclusions The regio- and stereospecific [2 + 2]-photoaddition of 1-pentyne to 16-dehydropregnenolone acetate has been used to obtain 2-propyl-16,17-cyclobuteno- and cyclobutanoprogesterones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.5, pp. 1184–1187, May, 1986.     

3，4—二氨基呋咱的乙酰化反应

研究了3，4—二氨基呋咱(DAF)的乙酰化反应，以DAF和溴乙酰溴缩合时成功地 得到了取代乙酰化呋咱衍生物，而和氯乙酰氯缩合时则发生呋咱环重排反应，两种 反应产物经叠氮化可得到不同的高氮含量含能化合物．文中分析了两种缩合反应中 呋咱环表现不同的原因．