- Friedelane triterpenoids: Transformations toward A-ring modifications including 2-: Homo derivatives
-
Friedelin and its derivatives, commonly known as friedelane triterpenoids, exhibit potential biological effects ranging from antimicrobial to anticancer to anti-HIV. To modify the A-ring of the pentacyclic triterpenoid, various transformative scopes have been utilized. Herein, some simple unprecedented transformative protocols have been accomplished towards furnishing 42 (25 new) A-ring modified pentacyclic friedelane triterpenoids. It is worth noting that the modifications include the all-new 2-homo derivatives. The one-pot BF3·OEt2-mediated oxidative transformation of friedelin to yield friedel-3-enol acetate as the major product was one of the key reactions. A group of isomeric A-ring modifications was produced on the basis of simple transformations on suitable friedelane-based molecules. The syntheses of the novel 2-homofriedelanes were envisioned from the transformative reactions of the designed triterpenoid 3-chlorofriedel-2-ene-2-carbaldehyde, which was isolated as the major product from the reaction of friedelin with the novel Vilsmeier-Haack reagent. New A-ring modified derivatives were also obtained due to further interesting transformations of 3-chlorofriedel-3-ene, isolated as side products from the same reaction. Again, considering the scope of the 3-chloro-2-enal moiety associated with the A-ring of the triterpenoid, some heterocycle-linked- (bonded to C3) 2-homofriedelane triterpenoids were synthesized. Various common reaction strategies were employed on suitable substrates to finally achieve a series of C2,C3-; C3,C4- and C2,C3,C4-functionalized as well as 2-homofriedelane triterpenoids with just one to four efficient steps.
- Das, Jayanta,Sarkar, Antara,Ghosh, Pranab
-
p. 6673 - 6688
(2018/05/07)
-
- Acetoxylation of friedelin by lead (IV) acetate and anti-octant behaviour of 2-acetoxyketones
-
Four products have been isolated by boron trifluoride-catalysed lead (IV) acetate acetoxylation of friedelin.Three of them have been characterized as 2α-acetoxyfriedelin, 4α-acetoxyfriedelin and 2β, 4α-diacetoxyfriedelin.The former has been efficiently converted into pachysandiol-A.Chiroptical measurements (CD) of these 2-acetoxyketones show considerable antioctant behaviour.
- Dutta, G.,Bose, S. N.
-
p. 975 - 977
(2007/10/02)
-
- Assignment of Carbon-13 Nuclear Magnetic Resonance Spectra of Some Friedelanes
-
Carbon-13 resonance assignments of cerin acetate, 2α-pyridine-N-oxyfriedelan-3-one, epi-cerin and its acetate, 3α-hydroxyfriedelan-2-one and its acetate, 3-hydroxyfriedel-3-en-2-one and its acetate, friedelane-3,7-dione, 3β- hydroxyfriedelan-7-one, canophyllol, friedelolactone and friedelolactone-2α-yl acetate, friedelane-2α,3α-diol and its diacetate, friedelane-2β,3α-diyl diacetate, pachysandiyl-A diacetate and friedelane-2β,3β-diyl diacetate have been made.The carbon signals of 3-oxofriedelan-29-ol and its acetate, methyl 3-oxofriedelan-29-oate, 3-oxofriedelan-30-ol, maytenfoliol, maytensifolin-A, maytensifiolin-B, pachysonol and pristimerin reported in the literature have also been considered for their specific resonance assignments.A few signal assignments of some friedelanes, viz. friedelan-28-ol, friedelan-29-ol, friedelan-30-ol, friedelan-29-al, 3-oxofriedelane-21α,26-diol and zeylasterone, reported recently by others, are unusual and have been reviewed.KEY WORDS 13C NMR Friedelanes Revised assignments
- Patra, Amarendra,Chaudhuri, Swapan Kumar
-
-