| Structure Identification: |
| Tetrahedron,2014,70(2):204–11. | | Asymmetric syntheses of (−)-isoretronecanol and (−)-trachelantamidine[Reference: WebLink] | Short and concise total asymmetric syntheses of (−)-Isoretronecanol and (−)-trachelantamidine are reported.
METHODS AND RESULTS:
Oxidative cleavage of tert-butyl (S,S,S,Z)-7-[N-benzyl-N-(α-methylbenzyl)amino]cyclohept-3-ene-1-carboxylate, followed by hydrogenolysis promoted in situ cyclisation/reduction, which provided rapid access to the bicyclic core within (−)-Isoretronecanol. Analogous treatment of the C(1)-epimer gave (−)-trachelantamidine.
CONCLUSIONS:
Overall, the syntheses of (−)-Isoretronecanol and (−)-trachelantamidine were completed in eight and seven steps and 20 and 9.5% yield, respectively, from commercially available starting materials. | | Tetrahedron Letters,2005,46(15);2691-3. | | The stereoselective addition of titanium(IV) enolates of 1,3-oxazolidin-2-one and 1,3-thiazolidine-2-thione to cyclic N-acyliminium ion. The total synthesis of (+)-isoretronecanol[Reference: WebLink] |
METHODS AND RESULTS:
(+)-Isoretronecanol (1) has been prepared in four steps and 36% overall yield via the diastereoselective addition of the titanium(IV) enolate derived from N-4-chlorobutyryl-1,3-thiazolidine-2-thione (3) to N-Boc-2-methoxypyrrolidine (5), which afforded 2-substituted pyrrolidine 7 in 84% yield (8:1 diastereoisomeric ratio), followed by reductive recovery of the chiral auxiliary and cyclization. | | Tetrahedron: Asymmetry,2011,22(6):662–668. | | A common approach to pyrrolizidine and indolizidine alkaloids; formal synthesis of (−)-isoretronecanol, (−)-trachelanthamidine and an approach to the synthesis of (−)-5-epitashiromine and (−)-tashiromine[Reference: WebLink] |
METHODS AND RESULTS:
A common and short stereoselective route is described for the formal synthesis of pyrrolizidine alkaloids, (−)-Isoretronecanol and (−)-trachelanthamidine. An approach to the synthesis of indolizidine alkaloids (−)-5-epitashiromine and (−)-tashiromine utilizing ring closing metathesis is also described starting from commercially available and inexpensive l-proline. |
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