Sachiko Takao

Monitored aminolysis of 3-acylthiazolidine-2-thione : A new convenient synthesis of amide

Abstract 3-Acylthiazolidine-2-thiones ( 1 ) were easily prepared and they were treated with several amines in dichloromethane to give amides 4 in very high yields within a short time. Aminoalcohols and aminophenols were selectively converted into acylaminoalcohols and acylaminophenols, respectively, by this reaction. One can monitor the reaction by disappearance of the yellow color of the starting material 1 . Some amide alkaloids ( 1 5 – 1 8 ) have effectively been synthesized.

Stereoselective synthesis of the functionalized syn-1,3,5,7-tetraol

The syn-1,3,5,7-tetraol derivative 21 was synthesized with complete stereo-selection based on the stereoselective reduction of a six-membered β-keto hemiacetal and a subsequent hemiacetal ring opening.

Total synthesis of the macrocyclic spermidine alkaloids (±)-lunarine and (±)-lunaridine

Total syntheses of (±)-lunarine (1) and (±)-lunaridine (2) have been performed via aminolysis of the thiazolidine-2-thione diamide derivative (10) with spermidine (11).

Studies on the structure of some derivatives of 1,3-thiazolidine-2-thione and Δ2-1,3-thiazoline-2-thiol

Two types of reactions have been observed for the ambident anion of 1,3-thiazolidine-2-thione: regioselective N-acylation and S-alkylation. The structures of the products, amides and thioethers, were determined by X-ray crystallographic analysis and by assignment of the 13C n.m.r. chemical shifts. The regioselectivity of the reactions is rationalised in terms of the hard–soft acid-base principle and has been exemplified by model experiments.

Biosynthesis of natural products. Part 3. Syntheses of ent-[17-14C]kaur-16-en-20-ol from enmein and of ent-[17-14C]kaur-16-ene derivatives oxygenated at C-3 from ent-kaur-16-ene-3β,19-diol

ent-[17-14C]Kaur-16-en-20-ol (5b) was synthesised from enmein (3), and ent-[17-14C]kaur-16-en-3β-ol (6b), ent-[17-14C]kaur-16-en-3-one (7b), and ent-[17-14C]kaur-16-en-3α-ol (8b) were synthesised from ent-kaur-16-ene-3β,19-diol (9). These labelled compounds were required for the investigation on the biosynthetic route from ent-kaur-16-ene (1) into enmein (3) and oridonin (4).

Biosynthesis of natural products. Part 1. Incorporations of ent-kaur-16-ene and ent-kaur-16-en-15-one into enmein and oridonin

Incorporations of ent-kaur-16-ene (7a) and ent-kaur-16-en-15-one (14a) into enmein (1a) and oridonin (6a) by Isodon japonicus Hara have been demonstrated by tracer experiments with seven labelled ent-kaurene derivatives. Furthermore, evidence has been obtained that functionalisation of ent-kaur-16-ene at the allylic position C–15 proceeds through direct oxygenation.

Biosynthesis of the diterpenes enmein and oridonin from ent-16-kaurene

ent-16-Kaurene (3) has been shown by tracer experiments to be incroporated into enmein (1) and oridonin (2) in Isodon japonicus Hara.

Biosynthesis of natural products. Part 4. Biosynthesis of enmein and oridonin from mono- or di-oxygenated kaurenoids

Incorporation of mono-oxygenated ent-kaur-1 6-ene derivatives (6a), (7a), and (8a) and dioxygenated derivatives (9a) and (12a) into both enmein (3) and oridonin (4) and those of C-20 or C-3 oxygenated ent-kaurene derivatives (13a), (14a), (15a), and (16a) into (3) by Isodon japonicus Hara have been demonstrated by the tracer experiments using the corresponding labelled compounds. It is probable, on the basis of the experimental results, that the positions in (3) and (4) which are similarly oxygenated are not necessarily oxygenated simultanously at an early stage in the biosynthetic route from ent-kaurene (1). However, control of the biosynthesis of enmein (3) may be initiated by the introduction of the C-3 oxygen-function of ent-kaurene (1) at an early stage.

Biosynthesis of natural products. Part 2. Syntheses of 14C- or 3H-labelled ent-kaur-16-ene derivatives oxygenated at C-7, or at C-7 and C-15, from epicandicandiol

ent-Kaur-16-en-7α-ol (12a), ent-kaur-16-en-7-one (14a), ent-kaur-16-en-7β-ol (15a), ent-15-oxokaur-16-en-7α-ol (22a), and ent-kaur-16-ene-7,15-dione (23a), and the labelled compounds (12b), (14b), (14c), (15b), (22b), (23b), and (23c), which are required for the investigation on the biosynthetic route from ent-kaur-16-ene (1) into enmein (3) and oridonin (4), were synthesised from epicandicandiol (5).

Bioynthesis of enmein and oridonin from 15-oxygenated kaurenoids and 14-deoxyoridonin

Incorporation of ent-16-kauren-15-one (3f) into enmein (1a) and of 14-deoxyoridonin (2b) into oridonin (2a) have been demonstrated by tracer experiments.