Ladislav Lešetický

A new access to β-methyl substituted secondary alcohols. Application to the synthesis of 4-methylheptan-3-ol

Abstract All four stereoisomers of 4-methylheptan-3-ol were synthesized by a five-step route starting from 4-thianones. Key steps in the synthesis include: (a) reduction of 3-propyl-4-thianone to yield an easily separable isomeric mixture of cis - and trans -3-propyl-4-thianols; and (b) a highly efficient resolution of the particular cis / trans -isomers through a chromatographic separation of their respective esters with ( S )-chlorofluoroacetic acid. Subsequent hydrolysis and desulfurization gave the required compounds in 18% overall yield. All the stereoisomers are obtained with purities better than 90%.

Stability and distribution constants of thallium(I) dialkyldithiophosphates

Stability and distribution constants of thallium(I) chelates with dimethyl-, diethyl-, di-(n-propyl)-, di-(n-propyl)-, di-(i-propyl)-, di-(n-butyl)-, di-(i-butyl)-, di-(sec-butyl)- and di-(i-amyl)-dithiophosphoric acids have been radiometrically determined using ion-exchange and extraction methods. The length of the alkyl chain influences considerably the distribution constant, however, it has only a small effect on the stability constant.

A new intermediate for the rapid synthesis of N-isopropyl-p-/125I/- or p-/123I/ amphetamine

The triazene derivative of N-isopropylamphetamine XI, has been prepared in seven steps from amphetamine, as a new intermediate which is readily converted to N-isopropyl-p-iodoamphetamine /XII/. XI makes now possible the simple, rapid and regiospecific synthesis of /125I/- or /123I/-XII direct before the application.

Preparation of35S-labeled natural thiophene derivatives by biosynthesis inTagetes sp

Some35S labeled thiophene derivatives have been prepared by biosynthesis inin vitro cultures ofTagetes sp. A different sources of isotopic sulfur were tested and the best results were achieved with [35S] sodium sulfate. Elemental sulfur was not incorporated. Radiochemical yields were around 1%.

Radioiodination of amitriptyline by isotope exchange

The catalysed isotope exchange method was studied with the aim to elaborate the optimal procedure for labeling of amitriptyline with iodine125I. Besides the catalysts published, cuprous salts and ammonium sulphate, a series of transition metal complexes as catalysts were tested at different reaction conditions. The best result (91% radiochemical yield) was achieved with trans-chlorocarbonylbis-(triphenylphosphine) iridium complex (Vaska catalyst) and sonification.

Chlorofluoroacetic Acid Derivatives of Sterically Hindered Chiral Alcohols

(R)- and (S)-chlorofluoroacetic acids were found to be an alternative to the Moshers acid especially when it fails to esterify alcohols from steric reasons.