Some terpene and steroid hydantoins

Abstract

Repeat analyses gave persistently low carbon figures, the steroid hydantoins generally have been troublesome in this respect (cf. ref. 1).

IBiox[(−)-menthyl]: A Sterically Demanding Chiral NHC Ligand

“…Commercially available, enantiopure (−)-menthone was found to be an ideal starting point for the synthesis of the imidazolium salt and NHC precursor 1 ·HOTf ( 5 in Scheme ). Starting with a Bucherer reaction, (−)-menthone was converted to the corresponding hydantoin 2 , providing a single diastereomer after recrystallization . Its challenging hydrolysis was accomplished under vigorous conditions using aqueous sulfuric acid at 150 °C, and this was followed by reduction to the amino alcohol 3 .…”

“…Starting with a Bucherer reaction, (-)-menthone was converted to the corresponding hydantoin 2, providing a single diastereomer after recrystallization. 6 Its challenging hydrolysis was accomplished under vigorous conditions using aqueous sulfuric acid at 150 °C, and this was followed by reduction to the amino alcohol 3. Through an established protocol, 7 this amino alcohol was smoothly converted to bioxazoline 4 (Scheme 1).…”

Thermal and spectroscopic characterization of several derivatives containing a new organic ring system

“…An attempt to prepare the tropane-3,6-bis-spirohydantoin system by Bucherer-Berg reaction of compounds 8 led only to recovery of the starting material. Previous efforts by other authors [20] to transform diketones into dihydantoins were unsuccessful, and monohydantoins were the only isolated products. This fact was attributed to precipitation of the compounds from the reaction medium.…”

Stereochemistry of the Bucherer–Bergs and Strecker reactions of tropinone, cis-bicyclo[3.3.0]octan-3-one and cis-3,4-dimethylcyclopentanone

“…The only cyclopentane ketones thus far studied have been (+)-camphor and (f )-norcamphor (3,19). Tager and Christensen (20) showed by X-ray diffraction that the amino acid formed on hydrolysis of the Bucherer hydantoin from (f )-norcamphor had the carboxyl group exo, sterically more accessible (21), while the amino acid formed on hydrolysis of the Strecker amino nitrile had the carboxyl endo, sterically less accessible, in conformity with the EJ rule.…”