Melithasterols A-D (1-4), isolated from a gorgoinan coral Melithaea ocracea of Okinawa, were shown to be cholestane-, 24-methyl-
22
-dehydrocholestane-,
22
-dehydrocholestane-, and 24-methylenecholestane-derivatives. respectively, having a common
3
β,
7
α -dihydroxy-5α,
6
α-epoxy-Δ^
8
steroid nucleus. This was confirmed by direct comparison with the authentic sample prepared by lead tetra-acetate oxydation of cholest-
6
-ene-
3
β, 5α,
8
α-triol
3
-monoacetate. Twelve new polyhydroxysterols were isolated from an Alcyonium sp. (
7
,
8
,9), and Sclerophytum sp. (14,16,19
b
,20,21,
22
a,23,26,28) soft corals collected off the coasts of the Andaman and Nicobar Islands in the Indian Ocean. All the Sclerophytum sp. soft corals contained 17a or its 25-deacetyl derivative. Compounds
7
to 9 were identified as 24-methylenecholest-5-ene-
3
β, 16β-diol-
3
-0-α-L fucoside (
7
) and its
7
β-(
8
) and
7
α-hydroxy (9) derivatives. Compound 14 was shown to be 24S-24-methylcholest-5-ene-
3
β,25ξ,26-triol and was correlated to the known compound 15 by 5α,
6
β-glycolation. Compound 16 was shown to be 5β,
6
α-isomer of 17
b
, correlating to 17
b
by PCC oxidation followed by dehydration. Compound 19
b
was identified with 25-deacetyl derivative of the known compound lobosterol (19a) by hydrolysis of authentic lobosterol. Compounds 20 and 21 were shown to be
7
-dehydro-(20) and
22
E
-dehydro-(21) derivative of 17a and 17
b
, respectively, by comparisons of their spectral data with reference compounds. Compounds
22
a and 23 were 24S-methylcholestane-
3
β, 5α 25-triol-
6
-one 25-monoacetate (
22
a) and its 25-deacetoxyl derivative (23). Partial PCC oxidation of 17a afforded
22
a. Compounds 26 (andamansterol) and 28 (nicobarsterol) were shown to be gorgost-5-ene-
3
β, 9α. 11α, 21-tetrol and novel secosteroid, 11,21-cyclo-
B
-homo-11-oxa-9, 11-secoergostane-
3
β,
6
α, 12ξ-triol-9-one, respectively, by spectral analyses (H-HCOSY, HMQC, HMBC).
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