Mono-p-bromobenzoate

The structure of eucosterol (17), a novel spirocyclic nortriterpenoid from Eucomis spp., has been established by X-ray analysis of the mono-p-bromobenzoate.20 The loss of a terminal methyl group is unusual. 

The nor-ketone rudbeckianone (244) has been identified in Rudbeckia lacini-ata A very interesting new sesquiterpenoid ketone, (+)-bicyclohumulenone (245), has been isolated from the leafy liverwort Plagiochila acanthophylla subsp. japonica The structure and absolute stereochemistry of this compound were ascertained by X-ray crystallographic analysis of the mono-p-bromobenzoate of the derived triol (246). This ketone co-occurs with the two enantiomeric sesquiterpenoids (-)-maalioxide (247) and (+)-cyclocolerenone (248). 

Capaurimine (142) was prepared by a parallel route. " " The structure of capaurimine was also confirmed by an X-ray analysis of capaurimine mono-p-bromobenzoate. ... 

Ginkgolide A mono - p - bromobenzoate ethanol solvate (absolute configuration)... 

Nozaki, H., A. Matsuo, M. Nakayama, Y. Kushi, N. Kamijo, and S. Hayashi Structure and Absolute Configuration of a-Pompene. II. An X-Ray Analysis of the Mono-p-bromobenzoate of the Diol Derived from a-Pompene. Bull. Chem. Soc. Japan 51, 568 (1978). 

In the following, selected examples for these reactions are reported. Reaction a) has been discussed in some detail already in Section IV. C examples for reaction d) are found in Section VI. A. Selective transbutylation (reaction b)) was achieved for various mono-, di- and triethers or esters of calix[4]arene, leading to tri-, di- and mono-t-butyl calix[4]arene derivatives, from which the 0-aUtyl and especially the O-acyl residues can be cleaved again if desired, or necessary. A single f-butyl group was also eliminated from the tetramethyl ether of 2b , the pentamethyl ether of and the hepta(p-bromobenzoate) of 2e °. Various other partially debutylated derivatives of 2c have been prepared analogously . ... 

---