76527-41-8Relevant academic research and scientific papers
Synthesis of the spermidine alkaloids (-)-(2R,3R)- and (-)-(2R,3S)-3-hydroxycelacinnine: Macrocyclization with oxirane-ring opening and inversion via cyclic sulfamidates
Khanjin, Nikolai A.,Hesse, Manfred
, p. 2028 - 2057 (2007/10/03)
The two epimers (-)-1a and (-)-1b of the macrocyclic lactama kaloid 3-hydroxycelacinnine with the (2R,3R) and (2R,3S) absolute configurations, respectively, were synthesized by an alternative route involving macrocyclization with the regio- and stereoselective oxirane-ring opening by the terminal amino group (Schemes 2 and 6). Properly N-protected chiral trans-oxirane precursors provided (2R,3R)-macrocycles after a one-pot deprotection-macrocyclization step under moderate dilution (0.005-0.01M). The best yields (65-85%) were achieved with trifluoroacetyl protection. Macrocyclization of the corresponding cis-oxiranes was unsuccessful for steric reasons. Inversion at OH-C(3) via nucleophilic displacement of the cyclic sulfamidate derivative with NaNO2 led to (2R,3S)-macrocycles. The synthesized (-)-(2R,3S)-3-hydroxycelacinnine ((-)-1b) was identical to the natural alkaloid.
Synthesis of α,β-Epoxyacyl Azides and Their Rearrangement to Epoxy Isocyanates and 3- and 4-Oxazolin-2-ones
Lemmens, Jacques M.,Blommerde, Willem W. J. M.,Thijs, Lambertus,Zwanenburg, Binne
, p. 2231 - 2235 (2007/10/02)
The conversion of α,β-epoxy carboxylates 6 into α,β-epoxyacyl azides 4 proceeds either via reaction of the mixed anhydrides 7 with sodium azide or via reaction of epoxyacyl chlorides 8 with hydrazoic acid-pyridine.The latter method is preferred.The azides 4 undergo a smooth thermal Curtius rearrangement to give 4-oxazolin-2-ones 10 for the substrates 4a-h having a hydrogen atom at C(β).Monitoring this reaction by means of IR shows that the epoxy isocyanates 5 are intermediates.Intramolecular ring expansion of 5 then leads to 3-oxazolin-2-ones 9 that tautomerizeto the 4-isomers 10a-h.Epoxyacyl azides 4i,n-q, having no hydrogen atom at C(β), producing 3-oxazolin-2-ones 9i,n-q by a proton shift is not possible.The products 9i and 9q rapidly add water at the imine bond to give oxazolidin-2-ones 11.Epoxy isocyanate 5k is reasonable stable in solution; reaction with methanol affords urethane 12.
