The structure (2) of ( �)-pandamarine , the major alkaloid isolated from the leaves of Pandanus amaryllifolius Roxb., has been determined by an X-ray diffraction study. Diffractometer data at 295 K were refined by least-squares techniques to a residual of 0.049 2244 'observed' reflections). Crystals of (2) are triclinic, P1, a 13.077(2), b 9.857(5), c 7.214(2) �, α 106.91(3), β 96.22(2), γ 100.01(2)0, Z 2.

Recrystallization of an equimolar mixture of silver(I) perchlorate and 2,2′:6′,2″-terpyridine ( terpy ) from acetonitrile solution yields the golden yellow crystalline adduct shown by a room-temperature single-crystal X-ray study to be [Ag3( terpy )4][( MeCN )Ag( terpy )](ClO4)4. Crystals are triclinic, Pī , a 21.48(1), b 14.525(7), c 13.506(8) Ǻ, α 68.50(4), β 80.71(4), γ 81.66(4)°, Z 2 formula units; R was 0.045 for 9681 'observed' reflections. The complex helical cation is quasi- centrosymmetric with a collinear Ag3 array. The environment of the central silver atom is planar four-coordinate, two short Ag-N distances [(2.198(5), 2.188(5)Ǻ] arising from the nitrogen atoms of outer rings of a pair of twisted terpy ligands ; the other two sites are occupied by the nitrogen atoms of the central terpy rings which bifurcate to the other silver atoms [Ag(central)-N(central) 2.624(5), 2.818(5)Ǻ; Ag(outer)-N(central) 2.704(4), 2.640(4)Ǻ], which are also coordinated by the outer ring nitrogen of the two ligands [Ag-N, 2.266(5), 2.304(4) Ǻ]. Coplanar with the latter, each outer silver atom has a further tridentate terpy coordinated [Ag-N(central) 2.362(4), 2.381(4)Ǻ; Ag-N(outer) 2.403(6)-2.573(5)Ǻ]. The [( MeCN )Ag( terpy )]+ species is also quasi-planar, Ag- NCMe being 2.174(7)Ǻ, opposed to the central ring nitrogen [2.331(5)Ǻ; Ag-N(outer) being 2.399(7), 2.433(7)Ǻ].

The structure and relative stereochemistry of four new metabolites from Briareum steckei has been deduced from 2D-n.m.r. experiments at high field, and confirmed by a single-crystal X-ray determination of a minor metabolite. The new compounds are non-halogenated briaran derivatives: (1R*,2S*,3R*,5Z,7S*,8(17)Z,l0R*, llR *,12S*,14S*)- 3,14-diacetoxy- 11,12-epoxy- 18-oxobriara-5,8(17)-dien-2-yl butanoate (3), its 3-deacetoxy derivative (4), (1R*,2R*,4R*,5Z,7S*,8(17)Z,10R*, 11R *,12S*,14S*)-4,14-diacetoxy-11,12-epoxy-18-oxobriara-5,8(17)-dien-2-yl butanoate (5) and the related 2-propanoate (6). Single-crystal X-ray determinations were performed on (5) and (6).

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