Utilization of Industrial Waste Materials, 6. Utilization of Derivatives of the Bicyclic Proline Analog (all‐R)‐Octahydrocyclopenta[b]pyrrol‐2‐carboxylic Acid in the Stereoselective Synthesis

Abstract

Utilization of the industrial waste material benzyl (all-R)-cyclopenta[b]pyrrol-2-carboxylate l a or its derivatives lb, l c as chiral auxiliaries is described. Allylation of nitrothioacetamides, proceeding by initial S-allylation followed by a facile thio Claisen rearrangement, is accomplished with a diastereomeric ratio (dr) up to 85:15 using l a , b as auxiliaries in stoichiometric amounts. Another aspect of this report is the diastereoselective synthesis of optically active amines, starting from aldehydes, with optical purities (op) up to 99%. Again a derivative of l a was used as source of chirality. One of the most convincing methods for creating a new asymmetric center in a predictable configuration is the use of [3,3] sigmatropic rearrangements. The reason is that in such intramolecular rearrangements the favorable transition-state geometry can normally be predicted on the basis of the principles of conformational analysis [3].We were encouraged by the high distereoselectivity obtained with an (5')-proline derivative under remote stereocontrol of the thio Claisen rearrangementL41 using S-allylated derivatives of nitrothioacetarnide~[~~l. Therefore several other chiral auxiliaries were screened for chiral induction studies.

A New Class of Heterocycles: 1,4,3,5-Oxathiadiazepane 4,4-dioxides

“…In recent years, considerable attention was paid to compounds resulting from the condensation of substituted amino alcohols with aldehydes [ 20 , 21 , 22 , 23 , 24 ]. As outlined in Scheme 1 , the substituted amino alcohols ( N ’-benzyl- N -(2-hydroxyethyl)-proline or sarcosine sulfamides) 1c and 2c were prepared in a three-step reaction sequence starting from ( tert -butyloxycarbonylsulfonyl) L-amino acid methyl esters 1 and 2 .…”