Diisopropyl (2 S ,3 S )‐2,3‐ O ‐Isopropylidenetartrate

Abstract

Diisopropyl (2 S ,3 S )‐2,3‐ O ‐isopropylidenetartrate product: diisopropyl (2S,3S)‐2,3‐O‐isopropylidenetartrate byproduct: Ti(OCHMe2)4

Dynamic Combinatorial Chemistry

“…While acid catalysts such as p-toluenesulfonic, triflic, or camphorsulfonic acid have been used extensively for transesterifications in organic synthesis, these catalysts can cause substantial decomposition of building blocks. 59 Milder alternatives such as titanium tetralkyl derivatives 60,61 or tin tributyl alkoxides do not accelerate the reactions sufficiently to be useful for dynamic combinatorial chemistry. Base catalysis appears to be the most efficient exchange method.…”

Cyclic RGD‐Peptidomimetics Containing Bifunctional Diketopiperazine Scaffolds as New Potent Integrin Ligands

“…The dipeptide Arg(Mtr)‐GlyOMe was coupled to either DKP‐1 or DKP‐2 and the resulting tetrapeptide mimics, after Boc cleavage, were attached to Cbz‐Asp(O t Bu)‐OH. Transesterification of the glycine methyl ester to the corresponding benzyl ester11 and hydrogenolysis afforded the linear pentapeptide precursors which were subjected to macrolactamization (HATU,12 HOAT, collidine, DMF). The cis ‐macrolactam (containing DKP‐1 ) was obtained in good yield (61 %) under moderate dilution conditions (20 m M ), while the trans ‐macrolactam (containing DKP‐2 ) required high dilution (2 m M ) and was obtained in a passable 41–45 % yield.…”

Facile Synthesis of Bicyclic and Tricyclic Skeletons by Cycloisomerizations of Hept-1-en-6-ynes and 4,9-Diheteradodeca-1,11-dien-6-ynes, Followed by [4 + 2] Cycloadditions

“…In order to improve the yield of the lactone 11, treatment of 5 with methyl acrylate (7) under palladium catalysis conditions was carried out in the presence of 10 mol % of Ti(OiPr) 4 , which is known to catalyze transesterifications of esters with various alcohols under neutral conditions. [13] In this case, however, no lactone 11 was obtained, but only unidentified oligomeric and decomposition products. It may well be that, in the presence of Ti(OiPr) 4 , the dienyne 13 was initially formed by transesterification of methyl acrylate (7) with the diol 5, but the intermediate diene formed by cycloisomerization of 13 may then have failed to undergo the intramolecular DielsϪAlder reaction to the lactone, although there is no obvious reason for this failure, [14] except that 13 would have an unfavorable conformation in the ground state.…”