~ Pergamon PIh S0031-9422(97)00491-3 Phytochemistry, Vol. 47, No. 1, pp. 125-129, 1998 © 1997ElsevierScienceLtd. All rights reserved Printed in Great Britain 0031-9422/98 $19.00+0.00 CYCLOPEPTIDE ALKALOIDS OF SCUTIA BUXIFOLIA ADEMIR F. MOREL*, EMILIAC. S. MACHADO,JANE J. MOREIRA,ANTONIOS. MENEZES, MARCO m. MOSTARDEIRO,NILO ZANATTA and LUDGER A. WESSJOHANN t Departamento de Quimica, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil; t Institut for Organische Chemie, Universitit Minchen (LMU), Karlstrale 23, D-80333 Minchen, Germany (Received 11 March 1997) Key Word Index--Scutia buxifolia; Rhamnaceae; peptide alkaloids; scutianines-K and -L; chiral phase gas chromatography. Abstract--Two new peptide alkaloids, scutianines-K and -L were isolated from Scutia buxifolia, a plant growing in Brazil, Argentina and Uruguay. Their structures have been determined on the basis of spectroscopic studies. The stereochemistry of the N,N-dimethyl amino acid side-chain and the ring amino acid residues in both alkaloids have been assigned by gas chromatography employing modified cyclodextrins as chiral stationary phases. © 1997 Elsevier Science Ltd INTRODUCTION In continuation of our chemical studies on Scutia buxifolia [1, 2], we now report on the isolation and structural elucidation of two new peptide alkaloids (1 and 2) found together with six known peptide alka- loids [2]. Elucidation of the structures of I and 2 was largely achieved through the use of a combination of FAB mass, 1H and J3C NMR spectroscopy and some chemical transformations. RESULTS AND DISCUSSION Scutianine-K (1) was obtained as colourless crys- talline material. Positive ion FAB-mass spectroscopy gave a quasi-molecular ion peak [M+H] ÷ at m/z 585, corresponding to C3aH40N4Os. The base peak appeared at m/z 148, corresponding to C10H14 N, sug- gesting the presence of a N,N-dimethyl phenylalanine unit. The peaks at m/z 135 (CsHgNO) and 190 (CI2H16NO) indicate the presence of styrylamine and hydroxyleucine units, respectively. The fragment ions at m/z 107 (C7H70), 106 (C7H60) and 105 (C7H50) confirmed the presence of a fl-phenylserine unit in 1. The IH and 13C NMR spectral data of scutianine-K strongly suggest it to have a structure similar to those of scutianines D, E [3] and G [4]. The 1H NMR spectrum (CDC13, 400 MHz) of 1 showed two sets of three doublets. The first set at 6 0.96 (J17,19 = 6.6 Hz) and 1.23 (J17,~8 = 6.6 Hz) was assigned to the C-19 and C-18 methyl protons, respec- * Author to whom correspondence should be addressed. 26 14 13 15 16 / .9 _9_/. ,9' 0 HN2o HN~7o r-z--x 23~'~22 lid ____~ 33,34 27 (1) tively. The double doublet at 6 4.55 (-/6.7= 8.3 Hz, J7,28 = 1.2 Hz) was assigned to the C-7 methine proton. The C-3 and C-4 methine protons appeared as double doublets at 6 4.94 (J3,17 = 2.0 Hz; J3,4 = 7.0 Hz) and 4.46 (3"3,4= 7.0 Hz; J4,20 = 10.0 Hz), respec- tively. The C-22 methine proton appeared as a double doublet at 6 2.63 (J2z23= = 6.7 Hz; J22,23a = 5.7 Hz). The C- 11 olefinic proton appeared as a doublet at ~5 6.73 (J;i,10 = 7.6 Hz), whereas the other olefinic pro- ton at C-10 showed a double-doublet at ~ 6.68 (Jl0,11 : 7.6 Hz; Ji0,9 = 9.0 Hz). The NMR spectrum also permitted the assignment of all amide protons at 6 6.51 (NH-6), 6.45 (NH-9) and 7.52 (NH-20), as doublets with J = 8.3, 7.6 and 10.0 Hz, respectively. A singlet at 6 2.09 was assigned 125