Younus M. Sheikh

Steroids from sponges

Abstract The sponges Stelleta clarella Tethya aurantia, Lissodendoryx noxiosa, Haliclona permollis and Haliclona sp. were examined for steroids. All sponges contained C27-C29, Δ5, mono and diunsaturated sterols. In addition, the sponge Tethya aurantia contained Z - 24 - propylidene - cholest - 5- en -3β-ol (19) and the 5α,8α-peroxides of cholesta - 5,7 - dien - 3β - ol, ergosterol, ergosta - 5,7,24(28) - trien - 3β - ol and 24ξ - ethyl - cholesta - 5,7 - dien - 3β - ol (29, 30, 31 and 32). The sponge Stelleta clarella also contained 24 - nor - cholesta - 4,22 - dien - 3 - one (21), cholesta - 4,22 - dien - 3 - one (22), 24ξ - methyl - cholesta - 4,22 - dien - 3 - one (24), ergosta - 4,24(28) - dien - 3 - one (25), (E) - stigmasta - 4,24(28) - dien - 3 - one (28), 5α - cholestanol (5), 5α - ergostanol (7) and 5α - poriferastanol (9) The possible biosynthetic significance of these hitherto undescribed peroxides and enones from marine sources is discussed. A synthesis of 19 is also described.

Terpenoids—LXXI: Chemical studies of marine invertebrates—XIV. Four representatives of a novel sesquiterpene class—the capnellane skeleton

Abstract The isolation and complete structure determination of four marine sesquiterpenoids: Δ 9(12) -capnellene-8β,10α-diol ( 1 ), Δ 9(12) -capnellene-3β,8β,10α-triol ( 3 ), Δ 9(12) -capnellene-5α,8β,10α-triol ( 5 ), Δ 9(12) -capnellene-2ξ,8β,10α-triol ( 7 ) from the soft coral Capnella imbricata is described. These alcohols are the first members of a fundamentally new sesquiterpene class consisting of three 5-membered fused rings which we have named capnellane (A).

Synthesis of sterols with modified side chains

Abstract Synthesis of sterols with side chain containing from four to nine carbons are described.

Steroids from starfish

Abstract Starfish Linckia multifora, Protoreaster nodosus, Protoreaster lincki, Culcita schmideliana, Nardoa variolata and Acanthaster planci were examined for sterols and sapogenins. All asteroids contained cholestanol in addition to C 27 to C 30 mono and diunsaturated sterols. A planci contained largest amounts of 5α-cholesta-9(11), 20(22)-diene-3β, 6α-diol-23-one and 5α-pregn-9(11)-ene-3β,6α-diol-20-one whereas P. nodosus, P. lincki and C. schmideliana contained only small amounts. Neither pregnane nor cholestane genins were detected in L. Multifora and N. variolata .

Acansterol: a cyclopropane-containing marine sterol from Acanthaster planci

From an extract of Acanthaster planci a new cyclopropane-containing sterol has been isolated and its structure elucidated.

Bioconversion of lanosterol into holotoxingonin, a triterpenoid from the sea cucumber Stichopus californicus

Labelled lanosterol is converted 200 times more efficiently than labelled acetate into holotoxinogenin when administrated to the sea cucumber Stichopus californicus.

Addition of dichlorocarbene to steroidal olefins. Preparation of a stereoisomer of demethylgorgosterol, a cyclopropane-containing marine sterol

Dichlorocarbene generated by pyrolysis of sodium trichloroacetate added to the 24,28-double bond of 5α-stigmast-24(28)-ene [Δ24(28)-fucostene](6) but failed to add to either the 5,6- or 22,23-double bond of ergosta-5,22-dien-3β-ol (brassicasterol)(19). However, dichlorocarbene generated by reaction of sodium hydroxide with chloroform in the presence of benzyltriethylammonium bromide added from the β side to the 5,6-double bond of cholesteryl (9), stigmasteryl (12), and brassicasteryl (18) acetates, to the 7,8-double bond (from the α side) of cholest-7-en-3β-yl (10) and 5α-ergosta-7,22-dien-3β-yl (17) acetates, and to the 22,23-double bond of 5α-ergost-22-en-6β-yl (11) and brassicasteryl (18) acetates.