The 1,3-thiazole derivatives are considered heterocycles of special interest since
they possess important pharmacological activities1,2. The results of investigations
devoted to the synthesis of new tetra- and pentanorlabdane compounds containing
thiazole structural units/core are reported.
The key strengths of this research are: accessible and natural starting material,
labdane diterpenoid (-)-sclareol (1), which can be easily extracted from renewable
resources; high probability of biological activities and low toxicity, due to their natural
origin. The reported tetra- and pentanorlabdane hybrid derivatives 8-11 were prepared
by interaction of thiosemicarbazones 4-7 with 2-bromoacetophenone under depicted
conditions2. In turn, the intermediates 4-7 derived from known ketoester 2 and
drimenone 3, can be prepared from sclareol 1 in three and four steps, respectively
(Scheme 1).

Reagents: a. KOH, EtOH, 98%; b. NH2NHCSNH2 or NH2NHCSNHC6H5, EtOH, 71-85%;
c. C6H5COCH2Br, EtOH, 75-83%.
Scheme 1
The structures of reported compounds 4-11 have been fully confirmed by mean of
1H, 13C and 15N RMN analysis, and MS spectrometry.
References:
1. A. I. El-Shenawy. Russ. J. Bioorg. Chem, 2016, 42(1), 100–105.
2. R. M. Mohareb, W. W. Wardakhan, G. A. Elmegeed, R. M. S. Ashour. Steroids, 2012, 77,
1560-1569.