Download PDF
Synlett 2004(14): 2529-2532  
DOI: 10.1055/s-2004-834825
LETTER
© Georg Thieme Verlag Stuttgart · New York

An Efficient Transformation of (-)-Quinic Acid into Carba-l-rhamnose

Elena Valsecchia, Alessio Tacchia, Davide Prosperib, Federica Compostellac, Luigi Panza*a
a DISCAFF, Università del Piemonte Orientale, via Bovio, 6, 28100 Novara, Italy
Fax: +39(0321)375821; e-Mail: panza@pharm.unipmn.it;
b Istituto di Scienze e Tecnologie Molecolari - CNR, via Golgi 19, 20133 Milano, Italy
c Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Università di Milano, via Saldini, 50, 20133 Milano, Italy
Further Information

Publication History

Received 29 July 2004
Publication Date:
20 October 2004 (online)

    Permissions and Reprints All articles of this category

Abstract

A novel stereoselective synthesis of carba-l-rhamnose from (-)-quinic acid is described. The title compound is obtained with an appropriate pattern of protecting groups to be used for the preparation of Streptococcus pneumoniae type 19F capsular polysaccharide repeating unit.

Key words

carba-l-rhamnose - stereoselective synthesis - capsular polysaccharide - quinic acid - shikimic acid

13

All new compounds have been characterized by proton and carbon NMR, exact mass, and/or elemental analysis. Spectroscopic data for selected compounds:
5a-Carba-2,3- O -cyclohexylidene-1- O -naphtylmetyl-α- l-rhamno-pyranoside ( 11a): 1H NMR (300 MHz, CDCl3): δ = 1.05 (d, 3 H, J Me,5 = 6.0 Hz, Me), 1.30-1.80 (m, 12 H,
H-5a and 5 CH2), 1.80-2.00 (m, 1 H, H-5), 3.30 (dd, 1 H, J 3,4 = 7.7 Hz, J 4,5 = 9.9 Hz, H-4), 3.90 (br m, 1 H, H-1), 4.05 (dd, 1 H, J 2,3 = 5.8 Hz, J 3,4 = 7.7 Hz, H-3), 4.29 (br m, 1 H, H-2), 4.72 and 4.78 (ABq, 2 H, CH2-Nap), 7.20-7.90 (m, 7 H, Ar H). 13C NMR (75.4 MHz, CDCl3): δ = 18.21 (q, CH3), 23.81 (t), 24.17 (t), 25.13 (t), 30.06 (d, C-5), 32.60 (t), 35.41 (t), 38.10 (t), 71.32 (t), 74.15 (d), 76.71 (d), 78.12 (d), 80.22 (d), 109.74 (s), 125.99 (d), 126.24 (d, 2 C), 127.79 (d), 127.96 (d), 128.31 (d, 2 C), 133.09 (s), 133.37 (s), 135.77 (s). [α]D 25 +15.7 (c = 1, CHCl3). Mp 99.0-101.0 °C.
5a-Carba-1-naphtylmetyl-3,4-dibenzyl-α- l-rhamno-pyranoside (14a,b): 1H NMR (300 MHz, CDCl3): 1.10 (d, 3 H, J 6,5 = 6.6 Hz, H-6), 1.62 (dt, 1 H, J 5aA,5aB = J 5aA,5 = 14.5 Hz, J 5aA,1 = 2.5 Hz, H-5aA), 1.86 (dt, 1 H, J 5aA,5aB = 14.5 Hz, J 5aB,5 = J 5aB,1 = 2.7 Hz, H-5aB), 1.97-2.17 (m, 1 H, H-5), 2.58 (br s, 1 H, -OH), 3.39 (t, 1 H, J 3,4 = J 4,5 = 9.1 Hz, H-4), 3.80 (br m, 1 H, H-1), 3.86 (dd, 1 H, J 2,3 = 3.3 Hz, J 3,4 = 9.1 Hz, H-3), 4.19 (br t, 1 H, H-2), 4.55-5.00 (m, 6 H, 3 ABq, CH2-Nap and CH2-Bn), 7.10-8.00 (m, 17 H, Ar H). 13C NMR (75.4 MHz, CDCl3): δ = 18.34 (q, C-6), 31.78 (d,
C-5), 32.05 (t, C-5a), 69.74 (d), 71.20 (t), 72.69 (t), 75.43 (t), 76.16 (d), 82.33 (d), 83.32 (d), 125.71 (d), 125.96 (d), 126.15 (d), 126.25 (d), 127.64 (d), 127.83 (d), 127.92 (d), 127.99 (d), 128.02 (d, 2 C), 128.13 (d, 2 C), 128.24 (d), 128.47 (d, 2 C), 128.60 (d, 2 C), 133.08 (s), 133.40 (s), 136.20 (s), 138.51 (s), 139.14 (s). [α]D 25 -18.3 (c = 1, CHCl3).

15

The stereochemistry of compounds 11a and 11b was inferred from the coupling constants of the signal of H-C(4) in 1H NMR spectrum. In fact, H-C(4) appeared as a doublet of doublets for both compounds, but in 11a the 3 J were 7.7 Hz and 9.9 Hz, while in compound 11b the constants were 10.8 Hz and 3.2 Hz. Furthermore, H-C(4) in compound 13 appeared as a triplet with a 3 J of 9.9 Hz, clearly indicating the axial orientation of H-C(4) in a chair conformation of 13.