The structures of staphigine and staphirine. Two novel bisditerpene alkaloids from Delphinium staphisagria

The Use of Carbon-13 Nuclear Magnetic Resonance Spectroscopy in Natural Products Chemistry

“…Moreover, chemical shifts for alkaloid B (768) were reassigned. Further representatives for this class of compounds include staphirine (221), staphisagnine and staphisagrine (222). Partial assignments are indicated in the formula for staphigine (769) (221), a dimeric spirocyclic diterpene alkaloid.…”

“…The 13C n. m. r. spectra of the eudesmanolides granilin (213) and ivasperin (214) isolated from Ambrosia polystachya DC have been reported along with those of other naturally occurring ring-A hydroxylated isoalantolactones (215-218) (9/). The Use ofCarbon-13 Nuclear Magnetic Resonance Spectroscopy 18.7 108.9 In the furanosesquiterpenes (219)(220)(221)(222)(223)(224)(225)(226) a distinction between quaternary carbons C-7 and C-II was made on the basis of the residual longrange coupling involving proton C(12)-H. The spectrum of (224) was found to remain invariant within the range of temperatures from -90° C to + 100° C. This implies that the lO-membered ring probably exists as one single rigid conformer in solution (92). HO"~ >=0 (218) ::..…”

Stereocontrolled synthesis of highly functionalised spirocyclic pyrans

“…5, 6 Unfortunately, most of the methods currently available for the synthesis of spirocyclic pyrans tend to be substrate specific and afford a limited number of functional handles from which synthetic diversification can take place. [2][3][4][5][6] We would now like to report our efforts into the synthesis of highly functionalised spirocyclic pyran units starting from a-hydroxy furan building blocks taking advantage of a selective Achmatowicz rearrangement, followed by a stereoselective allylation and ring-closing metathesis (RCM) sequence (Fig. 1).…”

Biomimetic Total Synthesis of (±)-Carbocyclinone-534 Reveals Its Biosynthetic Pathway

“…1 Biosynthetically, some cyclopropanes are created through intramolecular Diels−Alder reaction (IMDA), for example, crispatene, 2 salvileucalin B, 3 mitrephorone A, 4 and staphirine. 5 A recent example is carbocyclinone-534 (6), 6 a new antibiotic produced after the metabolism of tapinarof (1), which is a topical nonsteroidal anti-inflammatory stilbene drug that has been approved in China to treat psoriasis and atopic dermatitis. 7 Recently, Crawford and co-workers isolated two stilbene dimers of tapinarof (1), duotap-520 (4) and carbocyclinone-534 (6), two metabolism products of tapinarof (1) produced by gammaproteobacterial Photorhabdus.…”

“…Nature has endowed the chemical world with a rich and diverse collection of cyclopropane-containing secondary metabolites . Biosynthetically, some cyclopropanes are created through intramolecular Diels–Alder reaction (IMDA), for example, crispatene, salvileucalin B, mitrephorone A, and staphirine . A recent example is carbocyclinone-534 ( 6 ), a new antibiotic produced after the metabolism of tapinarof ( 1 ), which is a topical nonsteroidal anti-inflammatory stilbene drug that has been approved in China to treat psoriasis and atopic dermatitis .…”