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The Combination of Diallylboration and Ring‐Closing Metathesis in the Synthesis of Spiro‐β‐Amino Alcohols and (±)‐Cephalotaxine
Author(s) -
Kuznetsov Nikolai Yu.,
Kolomnikova Galina D.,
Khrustalev Victor N.,
Golovanov Denis G.,
Bubnov Yuri N.
Publication year - 2008
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200800755
Subject(s) - chemistry , allylic rearrangement , ring closing metathesis , alcohol , hydrolysis , salt metathesis reaction , ring (chemistry) , alkaline hydrolysis , metathesis , allylic alcohol , solvent , amino acid , organic chemistry , stereochemistry , medicinal chemistry , catalysis , biochemistry , polymer , polymerization
A convenient and practical methodology for the preparation of various spiro‐β‐amino alcohols has been elaborated. The approach involves allylboration and ring‐closing methathesis to prepare spirobicyclic compounds and their subsequent modification to spiro‐β‐amino alcohols containing four‐ to six‐membered azacycles. N ‐Boc‐protected azaspirocyclic olefins reacted with NBS in solvent under reflux to give tricyclic bromocyclocarbamates. The structure of one of the bromides was established by single‐crystal X‐ray analysis. The dehydrobromination of the tricyclic bromides with t BuOK produced olefins in good yields, which underwent allylic‐type rearrangement in the presence of MgBr 2 · Et 2 O. Alkaline hydrolysis of the rearranged carbamates led to diastereomerically pure spiro‐β‐amino alcohols. The structure of the dimethyl‐substituted amino alcohol was proved by single‐crystal X‐ray analysis. rac ‐(5 R *,6 S *)‐1‐Azaspiro[4.4]non‐7‐en‐6‐ol was used in the formal synthesis of cephalotaxine.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)