Strategies for ansamycin antibiotics. asymmetric synthesis of the C(3)–C(21) subunit of herbimycin A
摘要:
The asymmetric synthesis of 25, which constitutes the C(3)-C(21) segment of the stereochemically complex ansa chain of herbimycin A (2) has been achieved. The approach features the furan-hydropyran transformations 7-->5 and 8-->6 and the fragment coupling of 5 and 6 to produce the trisubstituted alkene 4 with high stereoselectivity. Stereoselective addition of the aryl anion derived from 24, which possesses the novel BIPSOP protecting group for the primary amine function, to the lactol 22 then delivered 25 as the major product. (C) 1999 Elsevier Science Ltd. All rights reserved.
An efficient approach to the type III lepadin alkaloids (lepadins F and G) has been developed through a key Diels–Alderreaction, in which a novel ketolactone‐type dienophile with chiral diol unit is employed to generate the desirable all‐cis‐trisubstituted cyclohexene with excellent regio‐ and stereoselectivity control. The subsequent selective sulfonylation of the diol unit followed by SN2 cyclization
通过关键的Diels-Alder反应,开发了一种有效的III型Lepadin生物碱方法(Lepadins F和G),其中使用了一种具有手性二醇单元的新型酮内酯型亲二烯体,以生成理想的全顺式三取代环己烯具有出色的区域和立体选择性控制。随后在氢化条件下对二醇单元进行选择性磺酰化,然后进行S N 2环化,可以构建取代的哌啶环。通过使用这种方法,( - ) - lepadin F从乙基合成升乳酸盐首次。
A Flexible Approach to the Synthesis of Type II and III Lepadin Alkaloids
作者:Xiaochuan Chen、Yue Hu、He Gu、Yuanliang Jia、Guiyin Luo
DOI:10.1055/a-1681-4067
日期:2022.3
A flexible approach to both type II and III lepadin alkaloids is developed for the first time. A key Diels–Alder reaction based on a novel chiral ketolactone dienophile is employed to obtain the desirable all-cis-trisubstituted cyclohexene with excellent regio- and stereoselectivity. As the subsequent closure of the piperidine ring is devised at the N1 and C2 position via an intramolecular nucleophilic