Absolute configuration of hydroazulenoid diterpenes based on circular dichroism

Cytotoxic Hydroazulene Diterpenes from the Brown Alga Cystoseira myrica

“…1) has been observed in other hydroazulene diterpenes. One particularly relevant example is dictyotadiol (9), whose relative configuration was deduced by x-ray analysis (Faulkner et al, 1977) and absolute configuration by circular dichroism studies (Arroyo et al, 1991 cyclopentenol moiety is also observed in a related hydroazulene diterpene (Wright et al, 1993, König et al, 1993. The hydroazulene skeleton is typical of diterpenoid metabolites derived from the brown algae of the genus Dictyota.…”

Four New Hydroazulenoid Diterpenes from the Tropical Marine Brown AlgaDictyota volubilis

“…Centers C-i, C-5, C-6, C-7, and C-9 were all determined to be as shown in I (Fig. 1) on the basis of interproton coupling information, 1H-NMR data comparisons made with 9-epi-dictyol (10) and dictyotriol (7, ii), as well as the results of a 2D NOESY measurement. The stereochemistry for C-il, C-i2, and C-i3 could not be assigned.…”

“…mt.) 359 ([M -i130r, 1), 316(1), 300 ([M -HOAc -1120], 2), 282 (4), 185 (6), 173 (8), 135 (10), 109 (40), 43 (100); HREIMS found 300.1999, C20H2502 requires 300.2090. graphy (6), followed by normal phase HPLC of the CH2C12 extract yielded four new (1)(2)(3)(4) and two previously reported diterpenes [5 (7) and dilophol (8, 9)1 (Fig. 1).…”

Marine natural products

“…(55) were determined by X-ray analysis and the structure of the unusual nor-diterpene (56) was elucidated by analysis of spectral data.66 As a result of the X-ray analysis of (53, the authors propose that the structures of (57), isolated previously from the same alga,65 and (58) from a North Queensland specimen of Dictyopteris d e l i ~u l a t a ~~ be revised to ( 59) and ( 60), respectively.66 A study of the metabolites of an Indian Ocean specimen of Dictyota divaricata resulted in the isolation of one known Amijiol (71) and three new dolastanes, dictinol (72), dictindiol (73), and dictintriol (74), were isolated from an Arabian Sea specimen of Dictyota indica and identified by interpretation of spectral data.69 Two investigations of an Australian collection of Dictyota divaricata have resulted in the isolation of diterpenes of several different structural classes. Initially, the structures of (2R,3R,4S,6E,9E, lOR)-4,17-dihydroxyxenic-6,9,13-trien-l-al-18-oic acid lactone (75), (2R,3R,6E,9E, 10R)-17-hydroxyxenic-6,9,13-trien-1 -al-18-oic acid lactone (76), (2R,3R,4S76R,7R, 9E, 10R)-4,17-dihydroxy-6,7-epoxyxenic-9,13-dien-1 -al-18-oic acid lactone (77), (2R,3R,4S,6E,9E, 10R)-17-acetoxy-4hydroxyxenic-6,9,13-trien-1,2-dial (78), 17-acetoxy-4ahydroxycrenulide (79), deacetoxydictyol H (80), and 2hydroxydictyoxide (8 1) were assigned by analysis of spectral data. 70 The same research group subsequently reported7' the structural elucidations of (2R*,3R*,6E,9E, lOR*, 18S*)- 17,18 : 18,19-bisepoxy-19-rnethoxyxenic-6,9,13-triene (82) and 502 NATURAL PRODUCT REPORTS, 1993 Full details of the syntheses of (+)-stoechospermol (92), 5(R), 15(R), 18-trihydroxyspata-l3,16(E)-diene (93), and (+)spatol (94), which are diterpenes from Stoechospermum m a r g i n a t ~m , ~~ Spatoglossum s ~h m i t t i i , ~~* ~~ and S. howleii,80 have been described in two consecutive papers.s1~82 The stereoselective synthesis of racemic 14-deoxyisoamijiol (95) from Dictyota lineariss3 has been accomplished using an intramolecular addition of an allylsilane to a conjugated dienone as the key transformati~n.~~ The total syntheses of (+)-isoamijiol (96), which is the optical antipode of a diterpene from Dictyota l i n e a r i ~, ~~ and ( +)-dolasta-1,(15),7,9-trien-l4-01 (97), the optical antipode of a metabolite from a mixture of D.…”