2,3,6,7-Tetrasubstituted Perhydroanthracenes: Stereoselective Synthesis and Biconformationality Studies

Abstract

2,3,6,7‐Tetrasubstituted perhydroanthracenes with the relative configuration 2β,3α,4aα,6β,7α,8aβ,9aα,10aβ have been synthesized stereoselectively. The biconformationality of these compounds has been investigated in solution by NMR and in the solid state by X‐ray crystallography. A triple‐ring flip 2 → 3 was realized for the first time by the covalently induced transition 29 → 30.

Asymmetric Synthesis of α-Substituted β-Amino Ketones from Sulfinimines (N-Sulfinyl Imines). Synthesis of the Indolizidine Alkaloid (−)-223A

“…A radical deoxygenation protocol proved to be successful. Treatment of indolizidine alcohol (+)- 29 with phenylthionochloroformate and pyridine in dichloromethane afforded the phenylthionocarbonate (−)- 31 in 55% isolated yield (Scheme ) . Reaction of tri - n -butyltin hydride and AIBN in benzene with (−)- 31 furnished indolizidine (−)-223A ( 9 ) in 74% yield with properties consistent with literature values …”

Two-Site Molecules as a Road for Engineering Complexity in Chemical Systems

“…In fact, all the values of the rate constants that were used throughout this paper for illustration fulfill the latter orders of magnitude making it possible to design artificial systems that would exhibit the present complex behaviors. In relation to future attempts to design microscopic structures, attention should be given to the fact that through-space and through-bond types of coupling are generally short range (<1 nm); thus, such an approach seems especially suitable when polycondensations between small monomeric units are used to synthesize the reactant R. One can, nevertheless, imagine much longer ranges to become accessible as soon as more-sophisticated structures, such as fused cycles, 39 or rigid secondary structures, such as those in proteins, are involved.…”

1,2-Diacetals: A New Opportunity for Organic Synthesis

“…Without the diacetal being present, the rings are oriented in such a way as to place the diol in a diaxial environment with the OTBDPS groups equatorial. 100 A particularly elegant application of BDA acting as a rigidifying template has been reported by Branchaud and co-workers in their studies toward (+)pancratistatin. In this work the BDA functions as both a diequatorial diol protecting group and a conformational lock; the reductive cyclization of 100 afforded the product without epimerization at the C2 position.…”