Synlett 2004(11): 2040-2042  
DOI: 10.1055/s-2004-830848
LETTER
© Georg Thieme Verlag Stuttgart · New York

Stereoselection of 3,4-cis and 3,4-trans Catechin and Catechin Condensation under Intramolecular Coupling Method [1]

Akiko Saito*a, Akira Tanakab, Makoto Ubukatac, Noriyuki Nakajima*d
a Biotechnology Center, Toyama Prefecture, Kosugi, Toyama 939-0398, Japan
b Department of Bioresources Science, College of Technology, Toyama Prefectural University, Kosugi, Toyama 939-0398, Japan
c Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan
d Biotechnology Center, Toyama Prefectural University, Kosugi, Toyama 939-0398, Japan
Fax: +81(766)567500; e-Mail: nori@pu-toyama.ac.jp;
Further Information

Publication History

Received 23 April 2004
Publication Date:
28 July 2004 (online)

Abstract

A high level of stereoselection between 3,4-cis and 3,4-trans catechin-catechin condensation under intramolecular coupling method has been realized by changing the diester linker between the nucleophile and the electrophile. The azelaic acid ­linker gave exclusively 3,4-trans catechin-catechin dimer, whereas glutaric acid linker gave 3,4-cis catechin-catechin dimer as the sole product.

1

This report is Part 7 in the series ‘Synthetic studies of proanthocyanidins’. For part 6 see ref. [7]

1

This report is Part 7 in the series ‘Synthetic studies of proanthocyanidins’. For part 6 see ref. [7]

12

Data for 23: To a solution of (2R,3S,4S)-5,7,3′,4′-tetra-benzyloxy-4-ethoxyethyloxy-flavan-3-yl (2R,3S)-5,7,3′,4′-tetrabenzyloxy-flavan-3-yl azelate (44 mg, 0.028 mmol) in CH2Cl2 (20 mL) was added dropwise TMSOTf (0.056 mL, 0.028 mmol, 0.5 M solution in CH2Cl2) at -20 °C. After stirring for 5 min, the pale yellow reaction mixture was quenched with sat. NaHCO3. The aq solution was extracted with CHCl3 and the combined organic phase were washed with H2O and brine, and dried (Na2SO4). Filtration, concentration and preparative silica gel TLC purification (hexane-EtOAc, 2:1) afforded 17 mg (0.012 mmol, 42%) of cyclic compound 23 as a single product. [α]D 25 -93.1 (c 0.34, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 7.40-7.18 (35 H, m), 7.06-6.93 (5 H, m), 6.84-6.76 (3 H, m), 6.56 (1 H, d, J = 2.2 Hz), 6.37 (1 H, d, J = 8.3 Hz), 6.10 (1 H, d, J = 2.1 Hz), 6.01 (1 H, dd, J = 9.6, 10.0 Hz), 6.00 (1 H, d, J = 2.1 Hz), 5.89 (1 H, s), 5.87 (1 H, dd, J = 2.2, 8.3 Hz), 5.36 (1 H, br s), 5.25-5.22 (1 H, m), 5.08-4.81 (8 H, m), 5.05 (1 H, d, J = 9.6 Hz), 4.86 (1 H, d, J = 11.9 Hz), 4.77 (1 H, d, J = 11.9 Hz), 4.75 (1 H, d, J = 11.4 Hz), 4.73 (1 H, d, J = 12.0 Hz), 4.68 (1 H, d, J = 10.0 Hz), 4.64 (1 H, d, J = 11.4 Hz), 4.61 (1 H, d, J = 11.7 Hz), 4.56 (1 H, d, J = 12.0 Hz), 4.46 (1 H, d, J = 11.7 Hz), 2.99-2.93 (1 H, m), 2.32-2.22 (1 H, m), 2.03 (1 H, dd, J = 2.4, 16.6 Hz), 1.97-1.90 (1 H, m), 1.84-1.74 (2 H, m), 1.25-0.80 (10 H, m). 13C NMR (100 MHz, CDCl3):
δ = 174.3, 171.4, 158.4, 157.5, 157.4, 155.7, 151.7, 148.9, 148.6, 148.51, 148.48, 138.0, 137.5, 137.31, 137.25, 137.21, 137.17, 136.9, 132.1, 130.8, 128.5-126.9 (C × 27), 121.0, 118.9, 117.1, 114.8, 114.6, 114.4, 112.0, 109.8, 108.2, 100.9, 94.8, 94.5, 90.4, 80.7, 71.6, 71.4, 71.11, 71.05, 70.2, 70.1, 70.0, 69.9, 69.0, 35.4, 34.4, 32.9, 29.7, 26.3, 24.9, 24.0, 23.0, 19.0. IR (neat): 3065 (w), 3032 (w), 2930 (m), 2862 (w), 2361 (w), 1732 (s), 1606 (s), 1512 (s), 1454 (s), 1379 (m), 1263 (m), 1213 (m), 1124 (s), 1026 (m), 910 (w), 851 (w), 812 (w), 737 (s), 696 (s) cm-1. FAB-MS: m/z = 1450.6 (81), 1451.6 (100) [M + H]+, 1452.6 (79), 1453.6 (43). FAB-HRMS: m/z calcd for C95H87O14 [M + H]+: 1451.6096. Found: 1451.6136.