bǔ
used in the transliteration of the names of organic compounds porphyrin 卟啉[bu3 lin2] and porphin 卟吩[bu3 fen1]
卟吩
bǔ fēn
porphin C20H14N4 (loanword)
卟啉
bǔ lín
porphyrin (organic chemical essential to hemoglobin and chlorophyll) (loanword)