4 research outputs found
Construction of the Myrioneuron Alkaloids: A Total Synthesis of (±)-Myrioneurinol
A strategy
has been developed that culminated in a stereoselective
total synthesis of the tetracyclic antimalarial Myrioneuron alkaloid myrioneurinol. The synthesis relies on three highly diastereoselective
reactions, including an intramolecular chelation-controlled Michael
spirocyclization of an <i>N</i>-Cbz-lactam titanium enolate
to an α,β-unsaturated ester for construction of the A/D-ring
system and the attendant C5 (quaternary), C6 relative stereochemistry;
a malonate enolate conjugate addition to a nitrosoalkene in order
to install the appropriate functionality and establish the configuration
at C7; and an intramolecular aza-Sakurai reaction to form the B-ring
and the accompanying C9 and C10 stereocenters
Total Syntheses of the Monoterpene Indole Alkaloids (±)-Alstilobanine A and E and (±)-Angustilodine
A synthetic
strategy has been developed culminating in stereoselective
total syntheses of the small class of unusual monoterpenoid indole
alkaloids exemplified by alstilobanines A (<b>3</b>) and E (<b>2</b>) and angustilodine (<b>1</b>). A pivotal step includes
a novel intermolecular Michael-type addition of an indole ester dianion
to a piperidine-derived nitrosoalkene to form the C15, C16 bond of
the alkaloids. In addition, an application of the Romo protocol for
effecting a stereoselective intramolecular nucleophile-assisted aldol-lactonization
was employed, leading to a β-lactone incorporating the requisite <i>cis</i>-fused 2-azadecalin moiety and also setting the C15,
C19, C20 relative stereochemistry of the metabolites. It was then
possible to stereoselectively effect an aldolization of a dianion
derived from this indole ester β-lactone intermediate with formaldehyde
to introduce the requisite C16 hydroxymethyl group. Further manipulations
of the system ultimately led to the three alkaloids in racemic form
Total Syntheses of the Monoterpene Indole Alkaloids (±)-Alstilobanine A and E and (±)-Angustilodine
A synthetic
strategy has been developed culminating in stereoselective
total syntheses of the small class of unusual monoterpenoid indole
alkaloids exemplified by alstilobanines A (<b>3</b>) and E (<b>2</b>) and angustilodine (<b>1</b>). A pivotal step includes
a novel intermolecular Michael-type addition of an indole ester dianion
to a piperidine-derived nitrosoalkene to form the C15, C16 bond of
the alkaloids. In addition, an application of the Romo protocol for
effecting a stereoselective intramolecular nucleophile-assisted aldol-lactonization
was employed, leading to a β-lactone incorporating the requisite <i>cis</i>-fused 2-azadecalin moiety and also setting the C15,
C19, C20 relative stereochemistry of the metabolites. It was then
possible to stereoselectively effect an aldolization of a dianion
derived from this indole ester β-lactone intermediate with formaldehyde
to introduce the requisite C16 hydroxymethyl group. Further manipulations
of the system ultimately led to the three alkaloids in racemic form
Visible-Light-Driven Photocatalytic Initiation of Radical Thiol–Ene Reactions Using Bismuth Oxide
A nontoxic and inexpensive
photocatalytic initiation of anti-Markovnikov
hydrothiolation of olefins using visible light is reported. This method
is characterized by low catalyst loading, thereby enabling a mild
and selective method for radical initiation in thiol–ene reactions
between a wide scope of olefins and thiols