Short total syntheses of both the putative and actual structures of the clerodane diterpenoid (+/-)-sacacarin by double annulation.
[reaction: see text] The putative structure of the naturally occurring clerodane diterpenoid (+/-)-sacacarin has been prepared in only 10 steps, six of which are C-C bond-forming steps, in a chemo-, regio-, and diastereoselective manner. The key part of the synthesis is the double annulation (double Michael, Pinner, and Dieckmann reaction) of a tethered carbon diacid and 3-butyn-2-one. A corrected structure for sacacarin is proposed, and the structure is proven by synthesis.
Stereocontrolled total synthesis of (+)-trans-dihydronarciclasine.
A highly stereoselective and efficient total synthesis of trans-dihydronarciclasine from a readily available chiral starting material was developed. The synthesis defines two of the five stereogenic centers of the natural product by an amino acid ester-enolate Claisen rearrangement. The other three stereogenic centers are created in a highly stereocontrolled fashion via a six-ring vinylogous ester intermediate, which is generated from the γ,δ-unsaturated ester functional group of the Claisen rearrangement product in an efficient three-step sequence. This concise total synthesis exemplifies the use of a highly regioselective Friedel-Crafts-type cyclization to form the B ring via an isocyanate intermediate derived from an N-Boc group, which is superior to the conventional method using an imino triflate intermediate. This same N-Boc group is employed to give high selectivity in the Claisen rearrangement earlier in the sequence.
Effects of Croton cajucara Extract on Serum Lipids of Rats Fed A High Fat Diet
The antihyperlipidaemic property of a hydroalcoholic extract obtained from the leaves of Croton cajucara Benth. (Euphorbiaceae) was studied in rats fed a high fat diet. Ten weeks following daily oral administration of plant extract (200 mg/kg), significant reductions in the serum total cholesterol (Tc), and low‐density lipoprotein cholesterol (LDL‐c) levels were observed without much change in serum high‐density lipoprotein cholesterol (HDL‐c) and triglycerides. The data also showed a significant elevation in the HDL‐c/Tc ratio in plant extract treated rats compared with the control group. The atherogenic index was significantly decreased by extract treatment. These beneficial effects and the absence of acute toxicity in C. cajucara extract may be of significance in the treatment of atherosclerosis.