Hydroxylactones esters

Fig. 2.128. HPLC-MS summed base peak mass chromatograms of total extracts of (a) T. weissflogii culture, (b) control, (c) faecal pellets immediately after grazing (48h) and (d) pellets after ageing in filtered seawater in the dark for 30 days. Peak identification a = phaeophorbide-a b = pyrophaeophorbide-a c = 132-chlorophyllone-a d = 132-epi-chlorophyllone-a (carotenoid) e + f = 132-hydroxyhlorophyll-a, 15 -hydroxylactone, chlorophyll-a g = chlorophyll-a g = chlorophyll-a epimer h = chlorophyll-a-like i = hydroxyphaeophytin-a + unknown i = hydroxyphaeophytin-a epimer j = phaeophytin-a j = phaeophytin-a epimer k = purpurin-18-phytyl ester 1 = pyrophaeophytin-a m = chlorine-a-like t = 132-oxopyrophaeophytin-a u = 132-oxopyrophaeophorbide a-24-methylcholesta-5,24(28)-dien-3/ -yl-ester SCE Sterol n = C272 d.b.a o = C27 2 d.b. +C28 2 d.b. p = C29 2 d.b. q = C27 1 d.b. r = C28 1 d.b. + C29 2 d.b. s = C29 2 d.b. Reprinted with permission from H. M. Talbot et al. [293], (ad.b = number of double bonds. = carotenoid.)...

Five- and six-membered /3-hydroxylactones have been synthesized diastereo- and (g) enantio-selectively from a,/l-unsaturated esters bearing a ketone tethered as the ester R group, in an intramolecular reductive aldol reaction catalysed by chiral bisphosphine complexes of copper .133... 

It is not necessary to have an all-carbon ring to preserve the cis geometry of a double bond. Lactones (cyclic esters) and cyclic anhydrides are useful too. A double bond in a five- or six-member ed compound must have a cis configuration and compounds like these are readily made. Dehydration of this hydroxylactone can give only a cis double bond and ring-opening with a nucleophile (alcohol, hydroxide, amine) gives an open-chain compound also with a cis double bond. The next section starts with an anhydride example. 

Acrylic acid, methyl ester 8.9 Hexanoic acid, 6-hydroxylactone 10.1... 

Butanoic acid, 4-hydroxylactone 12.6 Oxalic acid, dimethyl ester II.O... 

Solasodine (1) and related Solanum alkaloids are useful starting materials for the commercial preparation of steroid hormones." In particular the pregnane derivative (6) was prepared from solasodine in 65% overall yield via the intermediates (2), (3), and (4). The oxidative cleavage of the 20(22) double bond of pseudosolasodine diacetate (3), which is the least efficient step in this synthesis, has been investigated in more detail With sodium dichromate in acetic acid compound (3) gave the hydroxyester (5) and the hydroxylactone (7), in addition to the ester (4). Results of a kinetic study of this reaction were interpreted in terms of formation of hydroxyester (5) via allylic oxidation of pseudosolasodine diacetate prior to cleavage of the 20(22) double bond. ... 

Other Cycliaationa- The regio- and stereoselective intra-molecular ene reaotion of a glyoxalate ester (108) which gives the tricyclic hydroxylactone (109) is catalysed by SnCI. H ... 

A recently disclosed route to A -6,9-thia-PGI methyl ester (279) involved hydroxylation of the Corey lactone (2i) to give the hydroxylactone (276). Further transformations gave the benzoate (277) and henceforth the disulphide (278). Intramolecular addition of sulphenyl bromide followed by dehydro-... 

The strategy being pursued is guided by knowledge obtained during the structure elucidation that the hemilactal component of (140) (Scheme 34) exists in equilibrium with a-hydroxylactone forms such as (141) 103). One mode of disconnection of the latter (Scheme 34) leads sequentially to the glyoxylate ester (142) and thence to the meso dialdehyde (143). Actually, employment of (143) would yield a racemic product unless the aldehydic centres were differentiated as in the case of dinitro equivalent... 

Aroxyacoxy compds. a-Diketone monoketals Enolperoxides Glycidic acid esters a-Hydroxyacetals 1-Hydroxylactones a-Ketoacetals a-Keto-Y-lactones Lactolesters... 

This reaction sequence could be applied to the synthesis of the quassinoid analogs 15-0-P-octanoylglaucarubolone (98) and 15-0-P-3, 4 -dimethyl-2 -pentenoylglaucarubolone (99) (5). The latter, which has the bruceantin (53) ester side chain, was obtained by esterification of the hydroxylactone (95) with 3,4-dimethyl-2-pentenoic anhydride prepared by treatment of the corresponding acid with chlorosulfonyl isocyanate (35). 

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