Further Uses of Pyrrole‐Based Dienoxysilane Synthons: A Full Aldol Approach to Azabicyclo[x.2.1]alkane Systems

Abstract

Two racemic 2-azabicyclo[2.2.1]heptane structures, 15 and 21, and two chiral non-racemic 6-azabicyclo[3.2.1]octane representatives, 28 and 36, have been synthesized starting from 1-(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyloxy)-pyrrole (TBSOP, 5) and suitable ketones, 9, 16, 22 and 29. 2-Azabicycle 15 was then elaborated to racemic cyclopentane amino acid 38, while 6-azabicycle 36 served to access the enantiomerically pure normorphan-type structure 40. For all substrates, a uniform synthetic scheme was implemented based on the combination of two diastereoselective aldoltype carbon-carbon bond-forming reactions, the efficiencies

Vicarious Silylative Mukaiyama Aldol Reaction: A Vinylogous Extension

“…The structural identity of the tertiary carbinol TBS-ether anti - 5c (and hence of TMS- and TES-ethers anti - 5a and anti - 5b , by analogy) was ascertained by single crystal X-ray analysis showing a 5,1′- N , O - anti relative relationship, as recently reported by ourselves …”

“…The structural assignment of compounds 23 , 24 , and 25 was firmly ascertained by direct structural correlation to known substances, as detailed in the Experimental Section.…”

2-Azanorbornane – a versatile chiral aza-Diels–Alder cycloadduct: preparation, applications in stereoselective synthesis and biological activity

“…The synthesis of racemic derivatives of 2-azanorbornane starting from 1,2-substituted pyrrole was described by Zanardi et al, with aldol carbocyclization as a decisive step for the diastereoselective formation of a bicyclic skeleton. 48 Enantioselective preparation of 2-azanorbornanes made use of enantiopure starting materials. Grygorenko and co-workers proposed a novel synthetic route to both enantiomers of 2-azabicyclo[2.2.1]heptane-1-carboxylic acid 42, a rigid bicyclic proline analogue, based on a tandem cyanide addition-intramolecular cyclization.…”

Double Hetero-Michael Addition of N-Substituted Hydroxylamines to Quinone Monoketals: Synthesis of Bridged Isoxazolidines

“…Mo(CO) 6 -mediated cleavage of the N–O bond led to separable alcohol 6 (67%) and 7 (16%). From 6 , K 2 CO 3 -catalyzed trans-silylation afforded ketone 8 in 91% yield. Reduction of ketone 8 followed by acetylation gave two separable aminocyclitol derivatives 9 (47%) and its C-2 epimer 10 as a minor product (see the Supporting Information).…”