34 research outputs found
SEPARATION OF OPTICAL ISOMERS VIA DIASTEREOISOMERIC SALT FORMATION
The optical resolution processes were systematically investigated. The optimum of the
parameters of the diastereoisomeric salt formation can be determined by using a thermodynamic
equilibrium model. Based upon the conformational analysis of the structure for diastereo
isomeric salts, a new method has been elaborated for designing optical resolutions
Enhancement of Benzylic basicity by a fluorine substituent at the para- position: a case of lone pair/lone pair repulsion
The introduction of a halogen atom at any aromatic position of toluene considerably accelerates the base-promoted deprotonation of the methyl group. p-Fluorotoluene is the only exception; proton abstraction from its benzylic site occurs approximately at one tenth of the rate found with toluene (at -75 degrees C). Lone-pair repulsion appears to be at the origin of the decrease in acidity. Chloro- and bromotoluenes instantaneously exchange benzylic hydrogen against metal when treated with solution of lithium 2,2,6,6-tetramethylpiperidide (LITMP) in diethyl ether in the presence of potassium tert-butoxide and N,N,N',N",N"-pentamethyldiethylenetriamine at -100 degrees C. Due to extensive side reactions ("aryne" formation as a consequence of concomitant deprotonation of aromatic sites adjacent to the halogen atom), products can be isolated only in moderate yield (10-35%), but they are regioisomerically pure
First total synthesis of (+)-epogymnolactam, a novel autophagy inducer
A novel autophagy inducer, (+)-epogymnolactam (1), was first synthesized from cis-4-benzyloxy-2-butene-1-ol (2) in eight steps. A reliable preparation of optically pure epoxy alcohol (+)-3 from monobenzyl derivative (2) was established by a tandem strategy, Sharpless epoxidation/lipase kinetic resolution