Six unstable intramolecular diterpene esters were isolated from the seed oil of Jatropha curcas. Five of these, Jatropha factors C(2)-C(6) (3-7), are new natural products, and the structure of the known Jatropha factor C(1) (2) has been revised. All compounds possess the same diterpene moiety, namely, 12-deoxy-16-hydroxyphorbol (1). The dicarboxylic acid moieties of 2-5 contain a bicyclo[3.1.0]hexane unit, and those of 6 and 7 a cyclobutane unit, which is described for the first time within this compound class. Compounds 4 and 5 are C-8' epimers. The structures of 2-7 were elucidated by spectroscopic methods and give an insight into the biogenesis of the characterized substances.

No abstract

should be regarded as a binuclear sandwich complex having two four-electron donor p,q2-P2 ligands (i.e., 18 valence electrons (VE) per Rh atom), the bonding in the Co analogue 6 is more complicated. The X-ray structure analysis reveals two independent molecules per unit cell,1'21 each of whose Co-Co distances is ca. 3.1 A. In this case, the P,bridging ligand forms a "long" (similar to that of 2b) and a "short" (32-VE triple-decker with cyclo-P,?) rectangle, whose average P_P values correspond almost exactly to the distance of 2.38 A in the cubic (metallic) m~d i f i c a t i o n l '~~ of black phosphorus (z(P-P) = 2.45 A for 2b). The Rh-Rh' distance of 2b (3.324(1) A) is significantly longer than d ( M-M) for triple-decker complexes (2.63-2.73 A) containing a C~C I O -P~~~, middle deck and exhibiting metal-metal i n t e r a~t i o n ; [~.~] the average Rh-P value for 2b (2.416 A) is larger than that observed for 7 (2.335 A).[141 Experimental Procedure 2a.b: la (650mg, 2.2 mmol) [Isa] [lb (600 mg, 1.95 mmol) [I5b]] and P, (547 mg, 4.4 mmol) [483 mg, 3.9 mmol) were stirred in refluxing xylene (ca. 30 mL) for 8 h. The reaction solution (containing small amounts of insoluble components) was concentrated to 10 mL under oil-pump vacuum, treatedwith 3 g of AIZO3 (basic, activity II), and then dried under oil-pump vacuum to afford a freely flowing solid. Upon chromatography (column: 25 x 2.5 cm), excess P4 was eluted as a yellow forerun with pentane. Elution with pentane/toluene ( I : I ) then afforded Za,b as a yellow-orange fraction.After removal of the solvent under oil-pump vacuum, Za,b were obtained as spectroscopically pure, orange powders. Recrystallization from pentane (ca.-18°C) afforded Z a as needle-shaped and 2 b as cube-shaped, orange crystals. Yield Za: 207 mg (31Yo) [Zb: 190mg (3IYo)l.

Das bekannte, äußerst reaktive [18]Annulen 1 und das hypothetische Isomer 2 sollten sich durch CH2‐ und CHCH‐Gruppen als innere bzw. äußere Brücken stabilisieren lassen. Die entsprechenden Kohlenwasserstoffe 3 bzw. 4 sind nicht bekannt, obwohl sie als Bindeglieder zwischen den nicht‐natürlichen Annulenen und dem Porphyrin 5 bzw. dem kürzlich erstmals synthetisierten Porphycen 6 von großem Interesse sind. Gelungen ist jetzt die Herstellung der Tetraoxa‐Analoga von 5 und 6, d. h. der Dikationen 7 bzw. 8. Sie konnten in beiden Fällen als Perchlorate isoliert und strukturell charakterisiert werden, wobei ihre Verwandtschaft mit 5 bzw. 6 offen zu Tage trat. Während bei der Synthese von 7 der entscheidende Schritt eine MacDonald‐Kondensation war, der direkt eine Oxidation folgte, führte der Weg zu 8 über eine McMurry‐Kupplung mit anschließender Oxidation. Die Umsetzung von 2,2′‐Difurylmethan mit Formaldehyd ergab in geringer Ausbeute Tetraoxaporphyrinogen, das sich mit Salpetersäure tatsächlich zum Tetraoxaporphyrin oxidieren ließ.

Solid-phase and solution-phase protocols for the synthesis of furo[3,4-d]pyrimidines, pyrrolo[3,4-d]pyrimidines, and pyrimido[4,5-d]pyridazines are reported. The multistep solid-phase sequence involves the initial high-speed, microwave-promoted acetoacetylation of hydroxymethylpolystyrene resin with methyl 4-chloroacetoacetate. The immobilized 4-chloroacetoacetate precursor was subsequently subjected to three-component Biginelli-type condensations employing urea and a variety of aromatic aldehydes. The resulting 6-chloromethyl-functionalized resin-bound dihydropyrimidones served as common chemical platforms for the generation of the desired heterobicyclic scaffolds using three different traceless cyclative cleavage strategies. The corresponding furo[3,4-d]pyrimidines were obtained by microwave flash heating in a rapid, thermally triggered, cyclative release. Treatment of the chloromethyl dihydropyrimidone intermediates with a variety of primary amines followed by high-temperature microwave heating furnished the anticipated pyrrolo[3,4-d]pyrimidine scaffolds via nucleophilic cyclative cleavage. In a similar way, reaction with monosubstituted hydrazines resulted in the formation of pyrimido[4,5-d]pyridazines. All compounds were obtained in moderate to good overall yields and purities.