Application of Stereoselective Ether Transfer to the Synthesis of Isotactic Polyethers

Abstract

An efficient, convergent synthetic strategy has been developed which enables the synthesis of a series of naturally occurring isotactic polymethoxy compounds. Ether transfer followed by a hydride workup enables simultaneous, diastereoselective production of two methoxy centers in a single step. High yields and diastereoselectivity are observed even in stereochemically rich, polyoxygenated systems. Direct generation of bis-methyl ether moieties from methoxymethyl ethers minimizes the need for typical protective group strategies and the use of expensive methyl transfer reagents. Moreover, the simultaneous generation of a terminal primary iodide serves as a coupling partner for the generation of higher order congeners.

Chiral Pool Synthesis of N-Cbz-cis-(3R,4R)-3-methylamino-4-methylpiperidine from L-Malic acid

“…Aldehyde 6 was obtained from the reduction of ester 5 with DIBAL-H in excellent yield according to the literature procedure. 28,32,33 Over-reduction could be restrained by using 1.0-1.15 equivalent DIBAL-H employed and shorter reaction time (30 min). Moreover, the over-reduction product could be oxidized to aldehyde 6 with Dess-Martin reagent at rt in quantitative yield.…”

Stereoselective Isoxazolidine Synthesis Via Copper-Catalyzed Alkene Aminooxygenation

“…Hepta-1,6-dien-4-ol 13 was converted to 1j (162 mg, 26% yield, white solid). mp = 52–54 °C; 1 H NMR (400 MHz, CDCl 3 ), 7.81 (d, J = 8.0 Hz, 2H), 7.32 (d, J = 8.0 Hz, 2H), 6.84 (s, 1H), 5.84-5.73 (m, 1H), 5.10-5.05 (m, 4H), 4.20-4.16 (t, J = 6.0 Hz, 1H), 2.44 (s, 3H), 2.35-2.32 (m, 4H); 13 C NMR (75.5 MHz, CDCl 3 ) δ 144.8, 133.9, 133.6, 129.6, 128.4, 117.6, 85.0, 41.0, 36.6, 21.7; IR (thin film), 3220, 2929, 1642, 1334, 1168, 1091, 1019, 918, 814, 731 cm −1 ; HRMS (ESI) calcd.…”

Supersilyl Protective Groups in Aldol Reactions

“…This natural product is a linear carbon chain decorated with isotactic methoxy groups, which makes it challenging synthetic target. This natural product and related compounds have received considerable attention in the synthetic community [84][85][86][87][88][89][90]. Using super silyl aldol methods, 58 could be prepared from acetone, 3-butenal, three units of acetaldehyde SEE (1), and n-hexanal.…”