Synthesis of Enantiopure 4-Hydroxypipecolate and 4-Hydroxylysine Derivatives from a Common 4,6-Dioxopiperidinecarboxylate Precursor
摘要:
tert-Butyl 2-substituted 4,6-dioxo-1-piperidinecarboxylates 4 have been prepared in good yield starting from Boc-Asp-(OBu)-Bu-t and other beta-amino acids. By analogy with chiral tetramic acids, their reduction by NaBH4 in CH2Cl2/AcOH afforded the corresponding cis-4-hydroxy delta-lactams in good yield and stereoselectivity (68-98% de). In the absence of the A(1,3) strain (reduction of 6-substituted 2,4-dioxo-1-piperidines 7), the cis-4-hydroxy isomer was still obtained as the major product but the de values were consistently lower. 4-Hydroxy-6-oxo-1,2-piperidinedicarboxylate 2a, readily accessible from Boc-Asp-OtBu (three steps, 63% overall yield), has proven to be an excellent building block for the synthesis of cis- and trans-4-hydroxypipecolates 17 and 24 (52 and 36% overall yield, respectively) and for the synthesis of a protected 4-hydroxylysine derivative 29 (41% overall yield).
Regioselective synthesis of substituted piperidine-2,4-diones and their derivatives via Dieckmann cyclisations
作者:Charles M. Marson、Kin Cheung Yau
DOI:10.1016/j.tet.2015.06.052
日期:2015.9
A flexible route to piperidine-2,4-diones variously substituted at the 6-, 5,6- and 2,6-positions, both with and without 1-substitution, is described; no N-protective group is required. A related regioselective Dieckmann cyclisation is also described that uses Davies' α-methylbenzylamine auxiliary and affords 6-substituted piperidine-2,4-diones enantioselectively.