ASSEMBLY OF THE SOUTHERN MACROCYCLIC HALF OF (+)-SPIRASTRELLOLIDE A THROUGH CYCLIC ACETAL TETHERED RING-CLOSING METATHESIS AND 1,3-ANTI-MUKAIYAMA-ALDOL
摘要:
We describe herein details of our efforts in syntheses of A-ring and BC-ring of (+)-spirastrellolide A. While the former would constitute a facile 12-step synthetic endeavor starting from 1,5-pentanediol, the latter would showcase a cyclic acetal-tethered ring-closing metathesis [RCM] method that was developed in our lab for de novo synthesis of spiroketals. Constructing the entire Southern Half of the macrocycle would require 1,3-anti-Mukaiyama aldol addition for connecting A-ring and BC-ring specifically at C10 and C11, thereby culminating a 17-step approach for the Southern Macrocyclic Half linearly from (+)-2,3-(O)-iso-propylidene-L-threitol. Also discussed here is the possibility of pursuing a more convergent approach toward the assembly of the Southern Half through first connecting A-ring and C-ring via acetal formation that would first link together the free C13-OH with C17 at the spiro-BC-ring junction. An ensuing application of our cyclic acetal-tethered RCM strategy to close B-ring would adopt this cyclic acetal intermediate.
Development of a Method for the Reductive Cyclization of Enones by a Titanium Catalyst
作者:Natasha M. Kablaoui、Stephen L. Buchwald
DOI:10.1021/ja954192n
日期:1996.1.1
which bis(trimethylphosphine)titanocene is used to catalyze the reductive cyclization of enones to cyclopentanols via a metallacyclic intermediate has been developed. The key step in the process is the cleavage of the titanium−oxygen bond in the metallacycle by a silane to regenerate the catalyst. Mechanistic aspects of the reaction are discussed and the diastereoselectivity of the transformation is studied
Regio- and Enantioselective Iridium-Catalyzed Amination of Alkyl-Substituted Allylic Acetates with Secondary Amines
作者:Woo-Ok Jung、Minjin Yoo、Madyson M. Migliozzi、Jason R. Zbieg、Craig E. Stivala、Michael J. Krische
DOI:10.1021/acs.orglett.1c04135
日期:2022.1.14
Robust air-stable cyclometalated π-allyliridium C,O-benzoates modified by (S)-tol-BINAP catalyze the reaction of secondary aliphatic amines with racemic alkyl-substituted allylicacetates to furnish products of allylicamination with high levels of enantioselectivity. Complete branched regioselectivities were observed despite the formation of more highly substituted C–N bonds.
由 ( S )-tol-BINAP 改性的稳定的空气稳定环金属化 π-烯丙铱C , O-苯甲酸酯催化脂肪仲胺与外消旋烷基取代的烯丙乙酸酯的反应,提供具有高水平对映选择性的烯丙胺化产物。尽管形成了更高取代度的 C-N 键,但仍观察到完全支化的区域选择性。
Copper Catalyzed Asymmetric Synthesis of Chiral Allylic Esters
作者:Koen Geurts、Stephen P. Fletcher、Ben L. Feringa
DOI:10.1021/ja065780b
日期:2006.12.1
reagents to 3-bromopropenyl esters 1 to provide allylic esters 2 in high yields and high chemio-, regio-, and enantioselectivities. The work demonstrates that allylic asymmetric alkylation (AAA) can be done on substrates bearing a heteroatom at the gamma-position. The method is a practical route to chiral, nonracemic allylicalcohols. The use of functionalized substrates 1 or Grignard reagents leads to
8-Endo Cyclization of (Alkoxycarbonyl)methyl Radicals: Radical Ways for Preparation of Eight-Membered-Ring Lactones
作者:Eun Lee、Cheol Hwan Yoon、Tae Hee Lee、Sun Young Kim、Tae Joon Ha、Yong-suk Sung、Sang-Hyun Park、Sangyoub Lee
DOI:10.1021/ja980908d
日期:1998.8.1
Cyclization of (alkoxycarbonyl)methyl radicals generated from bromoacetates proceeds in the 8-endo mode to generate heptanolactones. Three distinct types of 8-endo/5-exo tandem radical cyclizations produce different bicyclic heptanolactones. In certain cases, intramolecularfree-radical attack on the heptanolactone carbonyl group initiates further skeletal rearrangement. Ab initio calculations indicate
The wittig rearrangement as a practical method for aldehyde synthesis
作者:Manfred Schlosser、Sven Strunk
DOI:10.1016/s0040-4020(01)80095-8
日期:1989.1
If the rearrangement of metalated allyl ethers 2 (or 4) is accomplished in the presence of potassium tert-butoxide, primary alkyl groups preferentially migrate to the unsubstituted allylic terminus (γ-position). Enolates 7 and 1-vinylalcoholates 6 (by alkyl migration to the α-position, adjacent to the oxygen atom) are produced in an approximate ratio of 9:1. Because of the endo-configuration of their